P3a(i) Speed

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Transcript P3a(i) Speed

Slide 1

www.PhysicsGCSE.co.uk

P3a(i) Speed
You will learn about:
How to calculate average speed and know its unit
How to measure speed
How a speed camera works

www.PhysicsGCSE.co.uk

Speed vs Average Speed

Careful… m/h means
metres per hour…

Speed is simply a measure of how fast an object is travelling.
Cars have speedometers that tell you the speed.
This can be in kilometres per hour, km/h, or
miles per hour, miles/h.

The Motorway has a speed limit of 70 miles/hour. This means the car can
legally cover 70 miles in one hour. You can see on the speedometer above
that 70 miles/h is the same as 110 km/h. This means that the car would
travel 110 kilometres in one hour.
A car never travels at the same speed all the time.
Traffic lights, speed limits and roundabouts force the driver to speed up
or slow down.
So we can work out the average speed of a car during its journey:

Average speed =

π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘šπ‘’ π‘‘π‘Žπ‘˜π‘’π‘›

with units metres per second, m/s, or kilometres per hour, km/h.

A car completes a 300km road trip in 4 hours.

A student takes 12 minutes to walk 1.4km to school

Its average speed is

Their average speed is

=

300π‘˜π‘š
4 β„Žπ‘œπ‘’π‘Ÿπ‘ 

π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘šπ‘’ π‘‘π‘Žπ‘˜π‘’π‘›

= 75 km/h

1400 π‘šπ‘’π‘‘π‘Ÿπ‘’π‘ 

π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘šπ‘’ π‘‘π‘Žπ‘˜π‘’π‘›

= 720 π‘ π‘’π‘π‘œπ‘›π‘‘π‘  = 1.94 m/s
1 km = 1000m so
1.4 km = 1400m

1 minute = 60 seconds so 12
minutes = 720 seconds

www.PhysicsGCSE.co.uk

How do speed cameras work?
The speed camera
takes a photo when
the car crosses the
first line…
… and the last line.
It records the time
taken between the
two photographs.
So, if the car crosses
the first line at
10.02 and 15
seconds and then
crosses the last line
at 10.02 and 20
seconds then the
camera knows it
took 5 seconds to
cross all the lines.

This is a speed
camera. It
measures speed.

There are the
white lines on
the road.

If there are 25 lines altogether then the total
distance is 25 x 1.5m = 37.5m

And we know that average speed is

π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘šπ‘’ π‘‘π‘Žπ‘˜π‘’π‘›

=

37.5 π‘š
5𝑠

= 7.5 m/s

This is about 17 miles per hour so under the 30 mile/h speed limit

The lines are usually
1.5 metres apart
from one another but
can be separated by
any distance.
In the UK we tend to
use 1.5 m

www.PhysicsGCSE.co.uk

How is average speed measured?
Average speed is usually measured over a much longer distance.
However, the principle is still the same as with the speed camera system.

A distance of 1
km is chosen.
Cameras like these take a photo of the car’s
numberplate at the beginning and at the end of the 1
km journey.

Each image carries a date and time stamp so a computer can work out the car’s average speed
between the two cameras.

Average speed cameras are better than standard
speed cameras because it means the driver
needs to drive more safely over a longer period
of time and distance.

www.PhysicsGCSE.co.uk

Rules about average speed, distance and time
Some Rules:
Average speed =

π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘šπ‘’ π‘‘π‘Žπ‘˜π‘’π‘›

This means that if the average speed of a car doubles then the time taken to complete the journey will be
halved.
Double the average speed = half the time taken
If the average speed of a car doubles then the car would have travelled twice as far
Double the average speed = Double the distance
If the average speed of the car doubles for twice the time the car travels for then the car will travel four
times as far
Double the average speed AND double the time = Four times the distance
Rules about Units:
1 km = 1000m
1 hour = 3600 seconds (60x60 = 3600)

108 km/h becomes

108,000 π‘šπ‘’π‘‘π‘Ÿπ‘’π‘ 
3600 π‘ π‘’π‘π‘œπ‘›π‘‘π‘ 

= 30 m/s

REMEMBER:
To change km/h into m/s: x1000 then Γ· 3600
To change m/s into km/h: Γ· 1000 then x 3600

www.PhysicsGCSE.co.uk

Instantaneous speed =
speed at an instant

Instantaneous speed

The speed at a particular instance is called the instantaneous speed.
Initial speed = u
Final speed = v
A racing car starts with a speed of u
and accelerates uniformly to v then:

the average speed =

Final and v start
with the same sound
so this is easy to
remember…

𝑒+𝑣
2

If we know the average speed of the racing car then we can also work out:
The distance in a certain time using

𝑒+𝑣 𝑑
2

How long it takes to travel a certain distance
π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
using π‘Žπ‘£π‘’π‘Ÿπ‘Žπ‘”π‘’ 𝑠𝑝𝑒𝑒𝑑 or
1
2

𝑒+𝑣 𝑑

So, increasing the average speed REDUCES the time taken to travel a particular distance.
Speed limits depend on the type of road (carriageway, motorway or outside a school) and
whether the area is urban or rural.

www.PhysicsGCSE.co.uk

Questions
1. Arjan ran 100 metres in 11.6 seconds. Billie ran 150 metres in
14.6 seconds. Who was fastest?
2. Jody flew an aeroplane over 1000 km. It took just 1.5 hours.
Calculate his average speed.
3. Why is it difficult (or impossible) to maintain a constant speed
over a journey?
4. Craig travels at a speed of 2 m/s. How long will it take him to
move 60 m?
5. The speed limit on motorways is 70 miles/h which is 112
km/h. If a driver drives 80 km in 45 minutes do they break the
speed limit?
6. A snail travels at a speed of 0.5 mm/s. How far does it go in
one hour?
7. A car reaches a speed of 85 km/h in 30 s starting from rest.
How fast does it go?

www.PhysicsGCSE.co.uk

Answers to Questions

1.

Arjan ran 100 metres in 11.6 seconds. Billie ran 150 metres in 14.6 seconds. Who was
fastest?
Arjan= 100m/11.6s = 8.62 m/s Billie = 150m/14.6s = 10.27 m/s Billie fastest

2.
3.
4.
5.

6.
7.

Jody flew an aeroplane over 1000 km. It took just 1.5 hours. Calculate his average speed.
1000 km / 1.5 hours = 666.67 km/h or 1000,000m / 5,400s = 185m/s
Why is it difficult (or impossible) to maintain a constant speed over a journey?
Obstacles such as roundabouts, traffic lights and pedestrians coupled with whether
the road is urban or rural prevents this.
Craig travels at a speed of 2 m/s. How long will it take him to move 60 m?
time = distance travelled / speed = 60m / 2m/s = 30s
The speed limit on motorways is 70 miles/h which is 112 km/h. If a driver drives 80 km in
45 minutes do they break the speed limit?
Speed = distance / time = 80km / 0.75 hour = 106.7 km/h so no the speed
limit is
not broken
A snail travels at a speed of 0.5 mm/s. How far does it go in one hour?
Distance = speed x time = 0.5mm x 3600s = 1800mm or 1.8m
A car reaches a speed of 85 km/h in 30 s starting from rest. How far does it go?
𝑒+𝑣 𝑑

The distance in a certain time using 2 we need to convert the units so they are the same
thus km/h needs to be in m/s as time is in seconds and distance needed to work out will be in
metres.
85km/h = 85x1000 then Γ·3600 = 23.6m/s
Using equation =

0π‘š/𝑠+23.6π‘š/𝑠 π‘₯ 30
=
2

354m


Slide 2

www.PhysicsGCSE.co.uk

P3a(i) Speed
You will learn about:
How to calculate average speed and know its unit
How to measure speed
How a speed camera works

www.PhysicsGCSE.co.uk

Speed vs Average Speed

Careful… m/h means
metres per hour…

Speed is simply a measure of how fast an object is travelling.
Cars have speedometers that tell you the speed.
This can be in kilometres per hour, km/h, or
miles per hour, miles/h.

The Motorway has a speed limit of 70 miles/hour. This means the car can
legally cover 70 miles in one hour. You can see on the speedometer above
that 70 miles/h is the same as 110 km/h. This means that the car would
travel 110 kilometres in one hour.
A car never travels at the same speed all the time.
Traffic lights, speed limits and roundabouts force the driver to speed up
or slow down.
So we can work out the average speed of a car during its journey:

Average speed =

π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘šπ‘’ π‘‘π‘Žπ‘˜π‘’π‘›

with units metres per second, m/s, or kilometres per hour, km/h.

A car completes a 300km road trip in 4 hours.

A student takes 12 minutes to walk 1.4km to school

Its average speed is

Their average speed is

=

300π‘˜π‘š
4 β„Žπ‘œπ‘’π‘Ÿπ‘ 

π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘šπ‘’ π‘‘π‘Žπ‘˜π‘’π‘›

= 75 km/h

1400 π‘šπ‘’π‘‘π‘Ÿπ‘’π‘ 

π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘šπ‘’ π‘‘π‘Žπ‘˜π‘’π‘›

= 720 π‘ π‘’π‘π‘œπ‘›π‘‘π‘  = 1.94 m/s
1 km = 1000m so
1.4 km = 1400m

1 minute = 60 seconds so 12
minutes = 720 seconds

www.PhysicsGCSE.co.uk

How do speed cameras work?
The speed camera
takes a photo when
the car crosses the
first line…
… and the last line.
It records the time
taken between the
two photographs.
So, if the car crosses
the first line at
10.02 and 15
seconds and then
crosses the last line
at 10.02 and 20
seconds then the
camera knows it
took 5 seconds to
cross all the lines.

This is a speed
camera. It
measures speed.

There are the
white lines on
the road.

If there are 25 lines altogether then the total
distance is 25 x 1.5m = 37.5m

And we know that average speed is

π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘šπ‘’ π‘‘π‘Žπ‘˜π‘’π‘›

=

37.5 π‘š
5𝑠

= 7.5 m/s

This is about 17 miles per hour so under the 30 mile/h speed limit

The lines are usually
1.5 metres apart
from one another but
can be separated by
any distance.
In the UK we tend to
use 1.5 m

www.PhysicsGCSE.co.uk

How is average speed measured?
Average speed is usually measured over a much longer distance.
However, the principle is still the same as with the speed camera system.

A distance of 1
km is chosen.
Cameras like these take a photo of the car’s
numberplate at the beginning and at the end of the 1
km journey.

Each image carries a date and time stamp so a computer can work out the car’s average speed
between the two cameras.

Average speed cameras are better than standard
speed cameras because it means the driver
needs to drive more safely over a longer period
of time and distance.

www.PhysicsGCSE.co.uk

Rules about average speed, distance and time
Some Rules:
Average speed =

π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘šπ‘’ π‘‘π‘Žπ‘˜π‘’π‘›

This means that if the average speed of a car doubles then the time taken to complete the journey will be
halved.
Double the average speed = half the time taken
If the average speed of a car doubles then the car would have travelled twice as far
Double the average speed = Double the distance
If the average speed of the car doubles for twice the time the car travels for then the car will travel four
times as far
Double the average speed AND double the time = Four times the distance
Rules about Units:
1 km = 1000m
1 hour = 3600 seconds (60x60 = 3600)

108 km/h becomes

108,000 π‘šπ‘’π‘‘π‘Ÿπ‘’π‘ 
3600 π‘ π‘’π‘π‘œπ‘›π‘‘π‘ 

= 30 m/s

REMEMBER:
To change km/h into m/s: x1000 then Γ· 3600
To change m/s into km/h: Γ· 1000 then x 3600

www.PhysicsGCSE.co.uk

Instantaneous speed =
speed at an instant

Instantaneous speed

The speed at a particular instance is called the instantaneous speed.
Initial speed = u
Final speed = v
A racing car starts with a speed of u
and accelerates uniformly to v then:

the average speed =

Final and v start
with the same sound
so this is easy to
remember…

𝑒+𝑣
2

If we know the average speed of the racing car then we can also work out:
The distance in a certain time using

𝑒+𝑣 𝑑
2

How long it takes to travel a certain distance
π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
using π‘Žπ‘£π‘’π‘Ÿπ‘Žπ‘”π‘’ 𝑠𝑝𝑒𝑒𝑑 or
1
2

𝑒+𝑣 𝑑

So, increasing the average speed REDUCES the time taken to travel a particular distance.
Speed limits depend on the type of road (carriageway, motorway or outside a school) and
whether the area is urban or rural.

www.PhysicsGCSE.co.uk

Questions
1. Arjan ran 100 metres in 11.6 seconds. Billie ran 150 metres in
14.6 seconds. Who was fastest?
2. Jody flew an aeroplane over 1000 km. It took just 1.5 hours.
Calculate his average speed.
3. Why is it difficult (or impossible) to maintain a constant speed
over a journey?
4. Craig travels at a speed of 2 m/s. How long will it take him to
move 60 m?
5. The speed limit on motorways is 70 miles/h which is 112
km/h. If a driver drives 80 km in 45 minutes do they break the
speed limit?
6. A snail travels at a speed of 0.5 mm/s. How far does it go in
one hour?
7. A car reaches a speed of 85 km/h in 30 s starting from rest.
How fast does it go?

www.PhysicsGCSE.co.uk

Answers to Questions

1.

Arjan ran 100 metres in 11.6 seconds. Billie ran 150 metres in 14.6 seconds. Who was
fastest?
Arjan= 100m/11.6s = 8.62 m/s Billie = 150m/14.6s = 10.27 m/s Billie fastest

2.
3.
4.
5.

6.
7.

Jody flew an aeroplane over 1000 km. It took just 1.5 hours. Calculate his average speed.
1000 km / 1.5 hours = 666.67 km/h or 1000,000m / 5,400s = 185m/s
Why is it difficult (or impossible) to maintain a constant speed over a journey?
Obstacles such as roundabouts, traffic lights and pedestrians coupled with whether
the road is urban or rural prevents this.
Craig travels at a speed of 2 m/s. How long will it take him to move 60 m?
time = distance travelled / speed = 60m / 2m/s = 30s
The speed limit on motorways is 70 miles/h which is 112 km/h. If a driver drives 80 km in
45 minutes do they break the speed limit?
Speed = distance / time = 80km / 0.75 hour = 106.7 km/h so no the speed
limit is
not broken
A snail travels at a speed of 0.5 mm/s. How far does it go in one hour?
Distance = speed x time = 0.5mm x 3600s = 1800mm or 1.8m
A car reaches a speed of 85 km/h in 30 s starting from rest. How far does it go?
𝑒+𝑣 𝑑

The distance in a certain time using 2 we need to convert the units so they are the same
thus km/h needs to be in m/s as time is in seconds and distance needed to work out will be in
metres.
85km/h = 85x1000 then Γ·3600 = 23.6m/s
Using equation =

0π‘š/𝑠+23.6π‘š/𝑠 π‘₯ 30
=
2

354m


Slide 3

www.PhysicsGCSE.co.uk

P3a(i) Speed
You will learn about:
How to calculate average speed and know its unit
How to measure speed
How a speed camera works

www.PhysicsGCSE.co.uk

Speed vs Average Speed

Careful… m/h means
metres per hour…

Speed is simply a measure of how fast an object is travelling.
Cars have speedometers that tell you the speed.
This can be in kilometres per hour, km/h, or
miles per hour, miles/h.

The Motorway has a speed limit of 70 miles/hour. This means the car can
legally cover 70 miles in one hour. You can see on the speedometer above
that 70 miles/h is the same as 110 km/h. This means that the car would
travel 110 kilometres in one hour.
A car never travels at the same speed all the time.
Traffic lights, speed limits and roundabouts force the driver to speed up
or slow down.
So we can work out the average speed of a car during its journey:

Average speed =

π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘šπ‘’ π‘‘π‘Žπ‘˜π‘’π‘›

with units metres per second, m/s, or kilometres per hour, km/h.

A car completes a 300km road trip in 4 hours.

A student takes 12 minutes to walk 1.4km to school

Its average speed is

Their average speed is

=

300π‘˜π‘š
4 β„Žπ‘œπ‘’π‘Ÿπ‘ 

π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘šπ‘’ π‘‘π‘Žπ‘˜π‘’π‘›

= 75 km/h

1400 π‘šπ‘’π‘‘π‘Ÿπ‘’π‘ 

π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘šπ‘’ π‘‘π‘Žπ‘˜π‘’π‘›

= 720 π‘ π‘’π‘π‘œπ‘›π‘‘π‘  = 1.94 m/s
1 km = 1000m so
1.4 km = 1400m

1 minute = 60 seconds so 12
minutes = 720 seconds

www.PhysicsGCSE.co.uk

How do speed cameras work?
The speed camera
takes a photo when
the car crosses the
first line…
… and the last line.
It records the time
taken between the
two photographs.
So, if the car crosses
the first line at
10.02 and 15
seconds and then
crosses the last line
at 10.02 and 20
seconds then the
camera knows it
took 5 seconds to
cross all the lines.

This is a speed
camera. It
measures speed.

There are the
white lines on
the road.

If there are 25 lines altogether then the total
distance is 25 x 1.5m = 37.5m

And we know that average speed is

π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘šπ‘’ π‘‘π‘Žπ‘˜π‘’π‘›

=

37.5 π‘š
5𝑠

= 7.5 m/s

This is about 17 miles per hour so under the 30 mile/h speed limit

The lines are usually
1.5 metres apart
from one another but
can be separated by
any distance.
In the UK we tend to
use 1.5 m

www.PhysicsGCSE.co.uk

How is average speed measured?
Average speed is usually measured over a much longer distance.
However, the principle is still the same as with the speed camera system.

A distance of 1
km is chosen.
Cameras like these take a photo of the car’s
numberplate at the beginning and at the end of the 1
km journey.

Each image carries a date and time stamp so a computer can work out the car’s average speed
between the two cameras.

Average speed cameras are better than standard
speed cameras because it means the driver
needs to drive more safely over a longer period
of time and distance.

www.PhysicsGCSE.co.uk

Rules about average speed, distance and time
Some Rules:
Average speed =

π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘šπ‘’ π‘‘π‘Žπ‘˜π‘’π‘›

This means that if the average speed of a car doubles then the time taken to complete the journey will be
halved.
Double the average speed = half the time taken
If the average speed of a car doubles then the car would have travelled twice as far
Double the average speed = Double the distance
If the average speed of the car doubles for twice the time the car travels for then the car will travel four
times as far
Double the average speed AND double the time = Four times the distance
Rules about Units:
1 km = 1000m
1 hour = 3600 seconds (60x60 = 3600)

108 km/h becomes

108,000 π‘šπ‘’π‘‘π‘Ÿπ‘’π‘ 
3600 π‘ π‘’π‘π‘œπ‘›π‘‘π‘ 

= 30 m/s

REMEMBER:
To change km/h into m/s: x1000 then Γ· 3600
To change m/s into km/h: Γ· 1000 then x 3600

www.PhysicsGCSE.co.uk

Instantaneous speed =
speed at an instant

Instantaneous speed

The speed at a particular instance is called the instantaneous speed.
Initial speed = u
Final speed = v
A racing car starts with a speed of u
and accelerates uniformly to v then:

the average speed =

Final and v start
with the same sound
so this is easy to
remember…

𝑒+𝑣
2

If we know the average speed of the racing car then we can also work out:
The distance in a certain time using

𝑒+𝑣 𝑑
2

How long it takes to travel a certain distance
π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
using π‘Žπ‘£π‘’π‘Ÿπ‘Žπ‘”π‘’ 𝑠𝑝𝑒𝑒𝑑 or
1
2

𝑒+𝑣 𝑑

So, increasing the average speed REDUCES the time taken to travel a particular distance.
Speed limits depend on the type of road (carriageway, motorway or outside a school) and
whether the area is urban or rural.

www.PhysicsGCSE.co.uk

Questions
1. Arjan ran 100 metres in 11.6 seconds. Billie ran 150 metres in
14.6 seconds. Who was fastest?
2. Jody flew an aeroplane over 1000 km. It took just 1.5 hours.
Calculate his average speed.
3. Why is it difficult (or impossible) to maintain a constant speed
over a journey?
4. Craig travels at a speed of 2 m/s. How long will it take him to
move 60 m?
5. The speed limit on motorways is 70 miles/h which is 112
km/h. If a driver drives 80 km in 45 minutes do they break the
speed limit?
6. A snail travels at a speed of 0.5 mm/s. How far does it go in
one hour?
7. A car reaches a speed of 85 km/h in 30 s starting from rest.
How fast does it go?

www.PhysicsGCSE.co.uk

Answers to Questions

1.

Arjan ran 100 metres in 11.6 seconds. Billie ran 150 metres in 14.6 seconds. Who was
fastest?
Arjan= 100m/11.6s = 8.62 m/s Billie = 150m/14.6s = 10.27 m/s Billie fastest

2.
3.
4.
5.

6.
7.

Jody flew an aeroplane over 1000 km. It took just 1.5 hours. Calculate his average speed.
1000 km / 1.5 hours = 666.67 km/h or 1000,000m / 5,400s = 185m/s
Why is it difficult (or impossible) to maintain a constant speed over a journey?
Obstacles such as roundabouts, traffic lights and pedestrians coupled with whether
the road is urban or rural prevents this.
Craig travels at a speed of 2 m/s. How long will it take him to move 60 m?
time = distance travelled / speed = 60m / 2m/s = 30s
The speed limit on motorways is 70 miles/h which is 112 km/h. If a driver drives 80 km in
45 minutes do they break the speed limit?
Speed = distance / time = 80km / 0.75 hour = 106.7 km/h so no the speed
limit is
not broken
A snail travels at a speed of 0.5 mm/s. How far does it go in one hour?
Distance = speed x time = 0.5mm x 3600s = 1800mm or 1.8m
A car reaches a speed of 85 km/h in 30 s starting from rest. How far does it go?
𝑒+𝑣 𝑑

The distance in a certain time using 2 we need to convert the units so they are the same
thus km/h needs to be in m/s as time is in seconds and distance needed to work out will be in
metres.
85km/h = 85x1000 then Γ·3600 = 23.6m/s
Using equation =

0π‘š/𝑠+23.6π‘š/𝑠 π‘₯ 30
=
2

354m


Slide 4

www.PhysicsGCSE.co.uk

P3a(i) Speed
You will learn about:
How to calculate average speed and know its unit
How to measure speed
How a speed camera works

www.PhysicsGCSE.co.uk

Speed vs Average Speed

Careful… m/h means
metres per hour…

Speed is simply a measure of how fast an object is travelling.
Cars have speedometers that tell you the speed.
This can be in kilometres per hour, km/h, or
miles per hour, miles/h.

The Motorway has a speed limit of 70 miles/hour. This means the car can
legally cover 70 miles in one hour. You can see on the speedometer above
that 70 miles/h is the same as 110 km/h. This means that the car would
travel 110 kilometres in one hour.
A car never travels at the same speed all the time.
Traffic lights, speed limits and roundabouts force the driver to speed up
or slow down.
So we can work out the average speed of a car during its journey:

Average speed =

π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘šπ‘’ π‘‘π‘Žπ‘˜π‘’π‘›

with units metres per second, m/s, or kilometres per hour, km/h.

A car completes a 300km road trip in 4 hours.

A student takes 12 minutes to walk 1.4km to school

Its average speed is

Their average speed is

=

300π‘˜π‘š
4 β„Žπ‘œπ‘’π‘Ÿπ‘ 

π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘šπ‘’ π‘‘π‘Žπ‘˜π‘’π‘›

= 75 km/h

1400 π‘šπ‘’π‘‘π‘Ÿπ‘’π‘ 

π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘šπ‘’ π‘‘π‘Žπ‘˜π‘’π‘›

= 720 π‘ π‘’π‘π‘œπ‘›π‘‘π‘  = 1.94 m/s
1 km = 1000m so
1.4 km = 1400m

1 minute = 60 seconds so 12
minutes = 720 seconds

www.PhysicsGCSE.co.uk

How do speed cameras work?
The speed camera
takes a photo when
the car crosses the
first line…
… and the last line.
It records the time
taken between the
two photographs.
So, if the car crosses
the first line at
10.02 and 15
seconds and then
crosses the last line
at 10.02 and 20
seconds then the
camera knows it
took 5 seconds to
cross all the lines.

This is a speed
camera. It
measures speed.

There are the
white lines on
the road.

If there are 25 lines altogether then the total
distance is 25 x 1.5m = 37.5m

And we know that average speed is

π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘šπ‘’ π‘‘π‘Žπ‘˜π‘’π‘›

=

37.5 π‘š
5𝑠

= 7.5 m/s

This is about 17 miles per hour so under the 30 mile/h speed limit

The lines are usually
1.5 metres apart
from one another but
can be separated by
any distance.
In the UK we tend to
use 1.5 m

www.PhysicsGCSE.co.uk

How is average speed measured?
Average speed is usually measured over a much longer distance.
However, the principle is still the same as with the speed camera system.

A distance of 1
km is chosen.
Cameras like these take a photo of the car’s
numberplate at the beginning and at the end of the 1
km journey.

Each image carries a date and time stamp so a computer can work out the car’s average speed
between the two cameras.

Average speed cameras are better than standard
speed cameras because it means the driver
needs to drive more safely over a longer period
of time and distance.

www.PhysicsGCSE.co.uk

Rules about average speed, distance and time
Some Rules:
Average speed =

π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘šπ‘’ π‘‘π‘Žπ‘˜π‘’π‘›

This means that if the average speed of a car doubles then the time taken to complete the journey will be
halved.
Double the average speed = half the time taken
If the average speed of a car doubles then the car would have travelled twice as far
Double the average speed = Double the distance
If the average speed of the car doubles for twice the time the car travels for then the car will travel four
times as far
Double the average speed AND double the time = Four times the distance
Rules about Units:
1 km = 1000m
1 hour = 3600 seconds (60x60 = 3600)

108 km/h becomes

108,000 π‘šπ‘’π‘‘π‘Ÿπ‘’π‘ 
3600 π‘ π‘’π‘π‘œπ‘›π‘‘π‘ 

= 30 m/s

REMEMBER:
To change km/h into m/s: x1000 then Γ· 3600
To change m/s into km/h: Γ· 1000 then x 3600

www.PhysicsGCSE.co.uk

Instantaneous speed =
speed at an instant

Instantaneous speed

The speed at a particular instance is called the instantaneous speed.
Initial speed = u
Final speed = v
A racing car starts with a speed of u
and accelerates uniformly to v then:

the average speed =

Final and v start
with the same sound
so this is easy to
remember…

𝑒+𝑣
2

If we know the average speed of the racing car then we can also work out:
The distance in a certain time using

𝑒+𝑣 𝑑
2

How long it takes to travel a certain distance
π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
using π‘Žπ‘£π‘’π‘Ÿπ‘Žπ‘”π‘’ 𝑠𝑝𝑒𝑒𝑑 or
1
2

𝑒+𝑣 𝑑

So, increasing the average speed REDUCES the time taken to travel a particular distance.
Speed limits depend on the type of road (carriageway, motorway or outside a school) and
whether the area is urban or rural.

www.PhysicsGCSE.co.uk

Questions
1. Arjan ran 100 metres in 11.6 seconds. Billie ran 150 metres in
14.6 seconds. Who was fastest?
2. Jody flew an aeroplane over 1000 km. It took just 1.5 hours.
Calculate his average speed.
3. Why is it difficult (or impossible) to maintain a constant speed
over a journey?
4. Craig travels at a speed of 2 m/s. How long will it take him to
move 60 m?
5. The speed limit on motorways is 70 miles/h which is 112
km/h. If a driver drives 80 km in 45 minutes do they break the
speed limit?
6. A snail travels at a speed of 0.5 mm/s. How far does it go in
one hour?
7. A car reaches a speed of 85 km/h in 30 s starting from rest.
How fast does it go?

www.PhysicsGCSE.co.uk

Answers to Questions

1.

Arjan ran 100 metres in 11.6 seconds. Billie ran 150 metres in 14.6 seconds. Who was
fastest?
Arjan= 100m/11.6s = 8.62 m/s Billie = 150m/14.6s = 10.27 m/s Billie fastest

2.
3.
4.
5.

6.
7.

Jody flew an aeroplane over 1000 km. It took just 1.5 hours. Calculate his average speed.
1000 km / 1.5 hours = 666.67 km/h or 1000,000m / 5,400s = 185m/s
Why is it difficult (or impossible) to maintain a constant speed over a journey?
Obstacles such as roundabouts, traffic lights and pedestrians coupled with whether
the road is urban or rural prevents this.
Craig travels at a speed of 2 m/s. How long will it take him to move 60 m?
time = distance travelled / speed = 60m / 2m/s = 30s
The speed limit on motorways is 70 miles/h which is 112 km/h. If a driver drives 80 km in
45 minutes do they break the speed limit?
Speed = distance / time = 80km / 0.75 hour = 106.7 km/h so no the speed
limit is
not broken
A snail travels at a speed of 0.5 mm/s. How far does it go in one hour?
Distance = speed x time = 0.5mm x 3600s = 1800mm or 1.8m
A car reaches a speed of 85 km/h in 30 s starting from rest. How far does it go?
𝑒+𝑣 𝑑

The distance in a certain time using 2 we need to convert the units so they are the same
thus km/h needs to be in m/s as time is in seconds and distance needed to work out will be in
metres.
85km/h = 85x1000 then Γ·3600 = 23.6m/s
Using equation =

0π‘š/𝑠+23.6π‘š/𝑠 π‘₯ 30
=
2

354m


Slide 5

www.PhysicsGCSE.co.uk

P3a(i) Speed
You will learn about:
How to calculate average speed and know its unit
How to measure speed
How a speed camera works

www.PhysicsGCSE.co.uk

Speed vs Average Speed

Careful… m/h means
metres per hour…

Speed is simply a measure of how fast an object is travelling.
Cars have speedometers that tell you the speed.
This can be in kilometres per hour, km/h, or
miles per hour, miles/h.

The Motorway has a speed limit of 70 miles/hour. This means the car can
legally cover 70 miles in one hour. You can see on the speedometer above
that 70 miles/h is the same as 110 km/h. This means that the car would
travel 110 kilometres in one hour.
A car never travels at the same speed all the time.
Traffic lights, speed limits and roundabouts force the driver to speed up
or slow down.
So we can work out the average speed of a car during its journey:

Average speed =

π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘šπ‘’ π‘‘π‘Žπ‘˜π‘’π‘›

with units metres per second, m/s, or kilometres per hour, km/h.

A car completes a 300km road trip in 4 hours.

A student takes 12 minutes to walk 1.4km to school

Its average speed is

Their average speed is

=

300π‘˜π‘š
4 β„Žπ‘œπ‘’π‘Ÿπ‘ 

π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘šπ‘’ π‘‘π‘Žπ‘˜π‘’π‘›

= 75 km/h

1400 π‘šπ‘’π‘‘π‘Ÿπ‘’π‘ 

π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘šπ‘’ π‘‘π‘Žπ‘˜π‘’π‘›

= 720 π‘ π‘’π‘π‘œπ‘›π‘‘π‘  = 1.94 m/s
1 km = 1000m so
1.4 km = 1400m

1 minute = 60 seconds so 12
minutes = 720 seconds

www.PhysicsGCSE.co.uk

How do speed cameras work?
The speed camera
takes a photo when
the car crosses the
first line…
… and the last line.
It records the time
taken between the
two photographs.
So, if the car crosses
the first line at
10.02 and 15
seconds and then
crosses the last line
at 10.02 and 20
seconds then the
camera knows it
took 5 seconds to
cross all the lines.

This is a speed
camera. It
measures speed.

There are the
white lines on
the road.

If there are 25 lines altogether then the total
distance is 25 x 1.5m = 37.5m

And we know that average speed is

π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘šπ‘’ π‘‘π‘Žπ‘˜π‘’π‘›

=

37.5 π‘š
5𝑠

= 7.5 m/s

This is about 17 miles per hour so under the 30 mile/h speed limit

The lines are usually
1.5 metres apart
from one another but
can be separated by
any distance.
In the UK we tend to
use 1.5 m

www.PhysicsGCSE.co.uk

How is average speed measured?
Average speed is usually measured over a much longer distance.
However, the principle is still the same as with the speed camera system.

A distance of 1
km is chosen.
Cameras like these take a photo of the car’s
numberplate at the beginning and at the end of the 1
km journey.

Each image carries a date and time stamp so a computer can work out the car’s average speed
between the two cameras.

Average speed cameras are better than standard
speed cameras because it means the driver
needs to drive more safely over a longer period
of time and distance.

www.PhysicsGCSE.co.uk

Rules about average speed, distance and time
Some Rules:
Average speed =

π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘šπ‘’ π‘‘π‘Žπ‘˜π‘’π‘›

This means that if the average speed of a car doubles then the time taken to complete the journey will be
halved.
Double the average speed = half the time taken
If the average speed of a car doubles then the car would have travelled twice as far
Double the average speed = Double the distance
If the average speed of the car doubles for twice the time the car travels for then the car will travel four
times as far
Double the average speed AND double the time = Four times the distance
Rules about Units:
1 km = 1000m
1 hour = 3600 seconds (60x60 = 3600)

108 km/h becomes

108,000 π‘šπ‘’π‘‘π‘Ÿπ‘’π‘ 
3600 π‘ π‘’π‘π‘œπ‘›π‘‘π‘ 

= 30 m/s

REMEMBER:
To change km/h into m/s: x1000 then Γ· 3600
To change m/s into km/h: Γ· 1000 then x 3600

www.PhysicsGCSE.co.uk

Instantaneous speed =
speed at an instant

Instantaneous speed

The speed at a particular instance is called the instantaneous speed.
Initial speed = u
Final speed = v
A racing car starts with a speed of u
and accelerates uniformly to v then:

the average speed =

Final and v start
with the same sound
so this is easy to
remember…

𝑒+𝑣
2

If we know the average speed of the racing car then we can also work out:
The distance in a certain time using

𝑒+𝑣 𝑑
2

How long it takes to travel a certain distance
π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
using π‘Žπ‘£π‘’π‘Ÿπ‘Žπ‘”π‘’ 𝑠𝑝𝑒𝑒𝑑 or
1
2

𝑒+𝑣 𝑑

So, increasing the average speed REDUCES the time taken to travel a particular distance.
Speed limits depend on the type of road (carriageway, motorway or outside a school) and
whether the area is urban or rural.

www.PhysicsGCSE.co.uk

Questions
1. Arjan ran 100 metres in 11.6 seconds. Billie ran 150 metres in
14.6 seconds. Who was fastest?
2. Jody flew an aeroplane over 1000 km. It took just 1.5 hours.
Calculate his average speed.
3. Why is it difficult (or impossible) to maintain a constant speed
over a journey?
4. Craig travels at a speed of 2 m/s. How long will it take him to
move 60 m?
5. The speed limit on motorways is 70 miles/h which is 112
km/h. If a driver drives 80 km in 45 minutes do they break the
speed limit?
6. A snail travels at a speed of 0.5 mm/s. How far does it go in
one hour?
7. A car reaches a speed of 85 km/h in 30 s starting from rest.
How fast does it go?

www.PhysicsGCSE.co.uk

Answers to Questions

1.

Arjan ran 100 metres in 11.6 seconds. Billie ran 150 metres in 14.6 seconds. Who was
fastest?
Arjan= 100m/11.6s = 8.62 m/s Billie = 150m/14.6s = 10.27 m/s Billie fastest

2.
3.
4.
5.

6.
7.

Jody flew an aeroplane over 1000 km. It took just 1.5 hours. Calculate his average speed.
1000 km / 1.5 hours = 666.67 km/h or 1000,000m / 5,400s = 185m/s
Why is it difficult (or impossible) to maintain a constant speed over a journey?
Obstacles such as roundabouts, traffic lights and pedestrians coupled with whether
the road is urban or rural prevents this.
Craig travels at a speed of 2 m/s. How long will it take him to move 60 m?
time = distance travelled / speed = 60m / 2m/s = 30s
The speed limit on motorways is 70 miles/h which is 112 km/h. If a driver drives 80 km in
45 minutes do they break the speed limit?
Speed = distance / time = 80km / 0.75 hour = 106.7 km/h so no the speed
limit is
not broken
A snail travels at a speed of 0.5 mm/s. How far does it go in one hour?
Distance = speed x time = 0.5mm x 3600s = 1800mm or 1.8m
A car reaches a speed of 85 km/h in 30 s starting from rest. How far does it go?
𝑒+𝑣 𝑑

The distance in a certain time using 2 we need to convert the units so they are the same
thus km/h needs to be in m/s as time is in seconds and distance needed to work out will be in
metres.
85km/h = 85x1000 then Γ·3600 = 23.6m/s
Using equation =

0π‘š/𝑠+23.6π‘š/𝑠 π‘₯ 30
=
2

354m


Slide 6

www.PhysicsGCSE.co.uk

P3a(i) Speed
You will learn about:
How to calculate average speed and know its unit
How to measure speed
How a speed camera works

www.PhysicsGCSE.co.uk

Speed vs Average Speed

Careful… m/h means
metres per hour…

Speed is simply a measure of how fast an object is travelling.
Cars have speedometers that tell you the speed.
This can be in kilometres per hour, km/h, or
miles per hour, miles/h.

The Motorway has a speed limit of 70 miles/hour. This means the car can
legally cover 70 miles in one hour. You can see on the speedometer above
that 70 miles/h is the same as 110 km/h. This means that the car would
travel 110 kilometres in one hour.
A car never travels at the same speed all the time.
Traffic lights, speed limits and roundabouts force the driver to speed up
or slow down.
So we can work out the average speed of a car during its journey:

Average speed =

π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘šπ‘’ π‘‘π‘Žπ‘˜π‘’π‘›

with units metres per second, m/s, or kilometres per hour, km/h.

A car completes a 300km road trip in 4 hours.

A student takes 12 minutes to walk 1.4km to school

Its average speed is

Their average speed is

=

300π‘˜π‘š
4 β„Žπ‘œπ‘’π‘Ÿπ‘ 

π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘šπ‘’ π‘‘π‘Žπ‘˜π‘’π‘›

= 75 km/h

1400 π‘šπ‘’π‘‘π‘Ÿπ‘’π‘ 

π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘šπ‘’ π‘‘π‘Žπ‘˜π‘’π‘›

= 720 π‘ π‘’π‘π‘œπ‘›π‘‘π‘  = 1.94 m/s
1 km = 1000m so
1.4 km = 1400m

1 minute = 60 seconds so 12
minutes = 720 seconds

www.PhysicsGCSE.co.uk

How do speed cameras work?
The speed camera
takes a photo when
the car crosses the
first line…
… and the last line.
It records the time
taken between the
two photographs.
So, if the car crosses
the first line at
10.02 and 15
seconds and then
crosses the last line
at 10.02 and 20
seconds then the
camera knows it
took 5 seconds to
cross all the lines.

This is a speed
camera. It
measures speed.

There are the
white lines on
the road.

If there are 25 lines altogether then the total
distance is 25 x 1.5m = 37.5m

And we know that average speed is

π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘šπ‘’ π‘‘π‘Žπ‘˜π‘’π‘›

=

37.5 π‘š
5𝑠

= 7.5 m/s

This is about 17 miles per hour so under the 30 mile/h speed limit

The lines are usually
1.5 metres apart
from one another but
can be separated by
any distance.
In the UK we tend to
use 1.5 m

www.PhysicsGCSE.co.uk

How is average speed measured?
Average speed is usually measured over a much longer distance.
However, the principle is still the same as with the speed camera system.

A distance of 1
km is chosen.
Cameras like these take a photo of the car’s
numberplate at the beginning and at the end of the 1
km journey.

Each image carries a date and time stamp so a computer can work out the car’s average speed
between the two cameras.

Average speed cameras are better than standard
speed cameras because it means the driver
needs to drive more safely over a longer period
of time and distance.

www.PhysicsGCSE.co.uk

Rules about average speed, distance and time
Some Rules:
Average speed =

π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘šπ‘’ π‘‘π‘Žπ‘˜π‘’π‘›

This means that if the average speed of a car doubles then the time taken to complete the journey will be
halved.
Double the average speed = half the time taken
If the average speed of a car doubles then the car would have travelled twice as far
Double the average speed = Double the distance
If the average speed of the car doubles for twice the time the car travels for then the car will travel four
times as far
Double the average speed AND double the time = Four times the distance
Rules about Units:
1 km = 1000m
1 hour = 3600 seconds (60x60 = 3600)

108 km/h becomes

108,000 π‘šπ‘’π‘‘π‘Ÿπ‘’π‘ 
3600 π‘ π‘’π‘π‘œπ‘›π‘‘π‘ 

= 30 m/s

REMEMBER:
To change km/h into m/s: x1000 then Γ· 3600
To change m/s into km/h: Γ· 1000 then x 3600

www.PhysicsGCSE.co.uk

Instantaneous speed =
speed at an instant

Instantaneous speed

The speed at a particular instance is called the instantaneous speed.
Initial speed = u
Final speed = v
A racing car starts with a speed of u
and accelerates uniformly to v then:

the average speed =

Final and v start
with the same sound
so this is easy to
remember…

𝑒+𝑣
2

If we know the average speed of the racing car then we can also work out:
The distance in a certain time using

𝑒+𝑣 𝑑
2

How long it takes to travel a certain distance
π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
using π‘Žπ‘£π‘’π‘Ÿπ‘Žπ‘”π‘’ 𝑠𝑝𝑒𝑒𝑑 or
1
2

𝑒+𝑣 𝑑

So, increasing the average speed REDUCES the time taken to travel a particular distance.
Speed limits depend on the type of road (carriageway, motorway or outside a school) and
whether the area is urban or rural.

www.PhysicsGCSE.co.uk

Questions
1. Arjan ran 100 metres in 11.6 seconds. Billie ran 150 metres in
14.6 seconds. Who was fastest?
2. Jody flew an aeroplane over 1000 km. It took just 1.5 hours.
Calculate his average speed.
3. Why is it difficult (or impossible) to maintain a constant speed
over a journey?
4. Craig travels at a speed of 2 m/s. How long will it take him to
move 60 m?
5. The speed limit on motorways is 70 miles/h which is 112
km/h. If a driver drives 80 km in 45 minutes do they break the
speed limit?
6. A snail travels at a speed of 0.5 mm/s. How far does it go in
one hour?
7. A car reaches a speed of 85 km/h in 30 s starting from rest.
How fast does it go?

www.PhysicsGCSE.co.uk

Answers to Questions

1.

Arjan ran 100 metres in 11.6 seconds. Billie ran 150 metres in 14.6 seconds. Who was
fastest?
Arjan= 100m/11.6s = 8.62 m/s Billie = 150m/14.6s = 10.27 m/s Billie fastest

2.
3.
4.
5.

6.
7.

Jody flew an aeroplane over 1000 km. It took just 1.5 hours. Calculate his average speed.
1000 km / 1.5 hours = 666.67 km/h or 1000,000m / 5,400s = 185m/s
Why is it difficult (or impossible) to maintain a constant speed over a journey?
Obstacles such as roundabouts, traffic lights and pedestrians coupled with whether
the road is urban or rural prevents this.
Craig travels at a speed of 2 m/s. How long will it take him to move 60 m?
time = distance travelled / speed = 60m / 2m/s = 30s
The speed limit on motorways is 70 miles/h which is 112 km/h. If a driver drives 80 km in
45 minutes do they break the speed limit?
Speed = distance / time = 80km / 0.75 hour = 106.7 km/h so no the speed
limit is
not broken
A snail travels at a speed of 0.5 mm/s. How far does it go in one hour?
Distance = speed x time = 0.5mm x 3600s = 1800mm or 1.8m
A car reaches a speed of 85 km/h in 30 s starting from rest. How far does it go?
𝑒+𝑣 𝑑

The distance in a certain time using 2 we need to convert the units so they are the same
thus km/h needs to be in m/s as time is in seconds and distance needed to work out will be in
metres.
85km/h = 85x1000 then Γ·3600 = 23.6m/s
Using equation =

0π‘š/𝑠+23.6π‘š/𝑠 π‘₯ 30
=
2

354m


Slide 7

www.PhysicsGCSE.co.uk

P3a(i) Speed
You will learn about:
How to calculate average speed and know its unit
How to measure speed
How a speed camera works

www.PhysicsGCSE.co.uk

Speed vs Average Speed

Careful… m/h means
metres per hour…

Speed is simply a measure of how fast an object is travelling.
Cars have speedometers that tell you the speed.
This can be in kilometres per hour, km/h, or
miles per hour, miles/h.

The Motorway has a speed limit of 70 miles/hour. This means the car can
legally cover 70 miles in one hour. You can see on the speedometer above
that 70 miles/h is the same as 110 km/h. This means that the car would
travel 110 kilometres in one hour.
A car never travels at the same speed all the time.
Traffic lights, speed limits and roundabouts force the driver to speed up
or slow down.
So we can work out the average speed of a car during its journey:

Average speed =

π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘šπ‘’ π‘‘π‘Žπ‘˜π‘’π‘›

with units metres per second, m/s, or kilometres per hour, km/h.

A car completes a 300km road trip in 4 hours.

A student takes 12 minutes to walk 1.4km to school

Its average speed is

Their average speed is

=

300π‘˜π‘š
4 β„Žπ‘œπ‘’π‘Ÿπ‘ 

π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘šπ‘’ π‘‘π‘Žπ‘˜π‘’π‘›

= 75 km/h

1400 π‘šπ‘’π‘‘π‘Ÿπ‘’π‘ 

π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘šπ‘’ π‘‘π‘Žπ‘˜π‘’π‘›

= 720 π‘ π‘’π‘π‘œπ‘›π‘‘π‘  = 1.94 m/s
1 km = 1000m so
1.4 km = 1400m

1 minute = 60 seconds so 12
minutes = 720 seconds

www.PhysicsGCSE.co.uk

How do speed cameras work?
The speed camera
takes a photo when
the car crosses the
first line…
… and the last line.
It records the time
taken between the
two photographs.
So, if the car crosses
the first line at
10.02 and 15
seconds and then
crosses the last line
at 10.02 and 20
seconds then the
camera knows it
took 5 seconds to
cross all the lines.

This is a speed
camera. It
measures speed.

There are the
white lines on
the road.

If there are 25 lines altogether then the total
distance is 25 x 1.5m = 37.5m

And we know that average speed is

π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘šπ‘’ π‘‘π‘Žπ‘˜π‘’π‘›

=

37.5 π‘š
5𝑠

= 7.5 m/s

This is about 17 miles per hour so under the 30 mile/h speed limit

The lines are usually
1.5 metres apart
from one another but
can be separated by
any distance.
In the UK we tend to
use 1.5 m

www.PhysicsGCSE.co.uk

How is average speed measured?
Average speed is usually measured over a much longer distance.
However, the principle is still the same as with the speed camera system.

A distance of 1
km is chosen.
Cameras like these take a photo of the car’s
numberplate at the beginning and at the end of the 1
km journey.

Each image carries a date and time stamp so a computer can work out the car’s average speed
between the two cameras.

Average speed cameras are better than standard
speed cameras because it means the driver
needs to drive more safely over a longer period
of time and distance.

www.PhysicsGCSE.co.uk

Rules about average speed, distance and time
Some Rules:
Average speed =

π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘šπ‘’ π‘‘π‘Žπ‘˜π‘’π‘›

This means that if the average speed of a car doubles then the time taken to complete the journey will be
halved.
Double the average speed = half the time taken
If the average speed of a car doubles then the car would have travelled twice as far
Double the average speed = Double the distance
If the average speed of the car doubles for twice the time the car travels for then the car will travel four
times as far
Double the average speed AND double the time = Four times the distance
Rules about Units:
1 km = 1000m
1 hour = 3600 seconds (60x60 = 3600)

108 km/h becomes

108,000 π‘šπ‘’π‘‘π‘Ÿπ‘’π‘ 
3600 π‘ π‘’π‘π‘œπ‘›π‘‘π‘ 

= 30 m/s

REMEMBER:
To change km/h into m/s: x1000 then Γ· 3600
To change m/s into km/h: Γ· 1000 then x 3600

www.PhysicsGCSE.co.uk

Instantaneous speed =
speed at an instant

Instantaneous speed

The speed at a particular instance is called the instantaneous speed.
Initial speed = u
Final speed = v
A racing car starts with a speed of u
and accelerates uniformly to v then:

the average speed =

Final and v start
with the same sound
so this is easy to
remember…

𝑒+𝑣
2

If we know the average speed of the racing car then we can also work out:
The distance in a certain time using

𝑒+𝑣 𝑑
2

How long it takes to travel a certain distance
π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
using π‘Žπ‘£π‘’π‘Ÿπ‘Žπ‘”π‘’ 𝑠𝑝𝑒𝑒𝑑 or
1
2

𝑒+𝑣 𝑑

So, increasing the average speed REDUCES the time taken to travel a particular distance.
Speed limits depend on the type of road (carriageway, motorway or outside a school) and
whether the area is urban or rural.

www.PhysicsGCSE.co.uk

Questions
1. Arjan ran 100 metres in 11.6 seconds. Billie ran 150 metres in
14.6 seconds. Who was fastest?
2. Jody flew an aeroplane over 1000 km. It took just 1.5 hours.
Calculate his average speed.
3. Why is it difficult (or impossible) to maintain a constant speed
over a journey?
4. Craig travels at a speed of 2 m/s. How long will it take him to
move 60 m?
5. The speed limit on motorways is 70 miles/h which is 112
km/h. If a driver drives 80 km in 45 minutes do they break the
speed limit?
6. A snail travels at a speed of 0.5 mm/s. How far does it go in
one hour?
7. A car reaches a speed of 85 km/h in 30 s starting from rest.
How fast does it go?

www.PhysicsGCSE.co.uk

Answers to Questions

1.

Arjan ran 100 metres in 11.6 seconds. Billie ran 150 metres in 14.6 seconds. Who was
fastest?
Arjan= 100m/11.6s = 8.62 m/s Billie = 150m/14.6s = 10.27 m/s Billie fastest

2.
3.
4.
5.

6.
7.

Jody flew an aeroplane over 1000 km. It took just 1.5 hours. Calculate his average speed.
1000 km / 1.5 hours = 666.67 km/h or 1000,000m / 5,400s = 185m/s
Why is it difficult (or impossible) to maintain a constant speed over a journey?
Obstacles such as roundabouts, traffic lights and pedestrians coupled with whether
the road is urban or rural prevents this.
Craig travels at a speed of 2 m/s. How long will it take him to move 60 m?
time = distance travelled / speed = 60m / 2m/s = 30s
The speed limit on motorways is 70 miles/h which is 112 km/h. If a driver drives 80 km in
45 minutes do they break the speed limit?
Speed = distance / time = 80km / 0.75 hour = 106.7 km/h so no the speed
limit is
not broken
A snail travels at a speed of 0.5 mm/s. How far does it go in one hour?
Distance = speed x time = 0.5mm x 3600s = 1800mm or 1.8m
A car reaches a speed of 85 km/h in 30 s starting from rest. How far does it go?
𝑒+𝑣 𝑑

The distance in a certain time using 2 we need to convert the units so they are the same
thus km/h needs to be in m/s as time is in seconds and distance needed to work out will be in
metres.
85km/h = 85x1000 then Γ·3600 = 23.6m/s
Using equation =

0π‘š/𝑠+23.6π‘š/𝑠 π‘₯ 30
=
2

354m


Slide 8

www.PhysicsGCSE.co.uk

P3a(i) Speed
You will learn about:
How to calculate average speed and know its unit
How to measure speed
How a speed camera works

www.PhysicsGCSE.co.uk

Speed vs Average Speed

Careful… m/h means
metres per hour…

Speed is simply a measure of how fast an object is travelling.
Cars have speedometers that tell you the speed.
This can be in kilometres per hour, km/h, or
miles per hour, miles/h.

The Motorway has a speed limit of 70 miles/hour. This means the car can
legally cover 70 miles in one hour. You can see on the speedometer above
that 70 miles/h is the same as 110 km/h. This means that the car would
travel 110 kilometres in one hour.
A car never travels at the same speed all the time.
Traffic lights, speed limits and roundabouts force the driver to speed up
or slow down.
So we can work out the average speed of a car during its journey:

Average speed =

π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘šπ‘’ π‘‘π‘Žπ‘˜π‘’π‘›

with units metres per second, m/s, or kilometres per hour, km/h.

A car completes a 300km road trip in 4 hours.

A student takes 12 minutes to walk 1.4km to school

Its average speed is

Their average speed is

=

300π‘˜π‘š
4 β„Žπ‘œπ‘’π‘Ÿπ‘ 

π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘šπ‘’ π‘‘π‘Žπ‘˜π‘’π‘›

= 75 km/h

1400 π‘šπ‘’π‘‘π‘Ÿπ‘’π‘ 

π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘šπ‘’ π‘‘π‘Žπ‘˜π‘’π‘›

= 720 π‘ π‘’π‘π‘œπ‘›π‘‘π‘  = 1.94 m/s
1 km = 1000m so
1.4 km = 1400m

1 minute = 60 seconds so 12
minutes = 720 seconds

www.PhysicsGCSE.co.uk

How do speed cameras work?
The speed camera
takes a photo when
the car crosses the
first line…
… and the last line.
It records the time
taken between the
two photographs.
So, if the car crosses
the first line at
10.02 and 15
seconds and then
crosses the last line
at 10.02 and 20
seconds then the
camera knows it
took 5 seconds to
cross all the lines.

This is a speed
camera. It
measures speed.

There are the
white lines on
the road.

If there are 25 lines altogether then the total
distance is 25 x 1.5m = 37.5m

And we know that average speed is

π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘šπ‘’ π‘‘π‘Žπ‘˜π‘’π‘›

=

37.5 π‘š
5𝑠

= 7.5 m/s

This is about 17 miles per hour so under the 30 mile/h speed limit

The lines are usually
1.5 metres apart
from one another but
can be separated by
any distance.
In the UK we tend to
use 1.5 m

www.PhysicsGCSE.co.uk

How is average speed measured?
Average speed is usually measured over a much longer distance.
However, the principle is still the same as with the speed camera system.

A distance of 1
km is chosen.
Cameras like these take a photo of the car’s
numberplate at the beginning and at the end of the 1
km journey.

Each image carries a date and time stamp so a computer can work out the car’s average speed
between the two cameras.

Average speed cameras are better than standard
speed cameras because it means the driver
needs to drive more safely over a longer period
of time and distance.

www.PhysicsGCSE.co.uk

Rules about average speed, distance and time
Some Rules:
Average speed =

π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘šπ‘’ π‘‘π‘Žπ‘˜π‘’π‘›

This means that if the average speed of a car doubles then the time taken to complete the journey will be
halved.
Double the average speed = half the time taken
If the average speed of a car doubles then the car would have travelled twice as far
Double the average speed = Double the distance
If the average speed of the car doubles for twice the time the car travels for then the car will travel four
times as far
Double the average speed AND double the time = Four times the distance
Rules about Units:
1 km = 1000m
1 hour = 3600 seconds (60x60 = 3600)

108 km/h becomes

108,000 π‘šπ‘’π‘‘π‘Ÿπ‘’π‘ 
3600 π‘ π‘’π‘π‘œπ‘›π‘‘π‘ 

= 30 m/s

REMEMBER:
To change km/h into m/s: x1000 then Γ· 3600
To change m/s into km/h: Γ· 1000 then x 3600

www.PhysicsGCSE.co.uk

Instantaneous speed =
speed at an instant

Instantaneous speed

The speed at a particular instance is called the instantaneous speed.
Initial speed = u
Final speed = v
A racing car starts with a speed of u
and accelerates uniformly to v then:

the average speed =

Final and v start
with the same sound
so this is easy to
remember…

𝑒+𝑣
2

If we know the average speed of the racing car then we can also work out:
The distance in a certain time using

𝑒+𝑣 𝑑
2

How long it takes to travel a certain distance
π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘’π‘™π‘™π‘’π‘‘
using π‘Žπ‘£π‘’π‘Ÿπ‘Žπ‘”π‘’ 𝑠𝑝𝑒𝑒𝑑 or
1
2

𝑒+𝑣 𝑑

So, increasing the average speed REDUCES the time taken to travel a particular distance.
Speed limits depend on the type of road (carriageway, motorway or outside a school) and
whether the area is urban or rural.

www.PhysicsGCSE.co.uk

Questions
1. Arjan ran 100 metres in 11.6 seconds. Billie ran 150 metres in
14.6 seconds. Who was fastest?
2. Jody flew an aeroplane over 1000 km. It took just 1.5 hours.
Calculate his average speed.
3. Why is it difficult (or impossible) to maintain a constant speed
over a journey?
4. Craig travels at a speed of 2 m/s. How long will it take him to
move 60 m?
5. The speed limit on motorways is 70 miles/h which is 112
km/h. If a driver drives 80 km in 45 minutes do they break the
speed limit?
6. A snail travels at a speed of 0.5 mm/s. How far does it go in
one hour?
7. A car reaches a speed of 85 km/h in 30 s starting from rest.
How fast does it go?

www.PhysicsGCSE.co.uk

Answers to Questions

1.

Arjan ran 100 metres in 11.6 seconds. Billie ran 150 metres in 14.6 seconds. Who was
fastest?
Arjan= 100m/11.6s = 8.62 m/s Billie = 150m/14.6s = 10.27 m/s Billie fastest

2.
3.
4.
5.

6.
7.

Jody flew an aeroplane over 1000 km. It took just 1.5 hours. Calculate his average speed.
1000 km / 1.5 hours = 666.67 km/h or 1000,000m / 5,400s = 185m/s
Why is it difficult (or impossible) to maintain a constant speed over a journey?
Obstacles such as roundabouts, traffic lights and pedestrians coupled with whether
the road is urban or rural prevents this.
Craig travels at a speed of 2 m/s. How long will it take him to move 60 m?
time = distance travelled / speed = 60m / 2m/s = 30s
The speed limit on motorways is 70 miles/h which is 112 km/h. If a driver drives 80 km in
45 minutes do they break the speed limit?
Speed = distance / time = 80km / 0.75 hour = 106.7 km/h so no the speed
limit is
not broken
A snail travels at a speed of 0.5 mm/s. How far does it go in one hour?
Distance = speed x time = 0.5mm x 3600s = 1800mm or 1.8m
A car reaches a speed of 85 km/h in 30 s starting from rest. How far does it go?
𝑒+𝑣 𝑑

The distance in a certain time using 2 we need to convert the units so they are the same
thus km/h needs to be in m/s as time is in seconds and distance needed to work out will be in
metres.
85km/h = 85x1000 then Γ·3600 = 23.6m/s
Using equation =

0π‘š/𝑠+23.6π‘š/𝑠 π‘₯ 30
=
2

354m