Transcript Chapter 15 GCSE Additional Science Interaction between objects Physics 2 Forces working in Pairs Force ‘A’ that you exert on the trolley. Force ‘B’ exerted by the trolley.

Chapter 15
GCSE Additional Science
Interaction
between objects
Physics 2
Forces working in Pairs
Force ‘A’ that you exert
on the trolley.
Force ‘B’ exerted by the trolley (on you) – it
is equal and opposite to force ‘A’.
Force B
Constant speed
Chapter 15
GCSE Additional Science
Force A
It doesn’t matter what direction you place the force
on the trolley, the trolley will place a force of the
same magnitude, but in the opposite direction. The
forces don’t cancel each other out, as the two
forces act on different bodies.
Work Done
Force (N)
As an object is moved, you do WORK and you have to
use energy.
To calculate the work done, you must use:
Chapter 15
GCSE Additional Science
Distance Force moved (m)
Work (J) = Force (N) x Distance Force moved (m)
W
F×d
Chapter 15
GCSE Additional Science
Example Questions
1. Sion pushes a block 5m across a table with a force of
5N. He tires and stops. How much work did Sion do?
25J
2. Anna lifts her school bag 2m up in the air with a force
of 10N. How many times did she do it?
20J
3. Mathew does 200J worth of work whilst pushing a box
with the force of 50N. What distance did he move the
box?
4m
4. Cai lifts his cat 1.5m into the air. If he had done 75J
worth of work, how much force did he use?
50N
5. Carl drives a car over 1000m. If the engine exerts a
force of 2000N, how much work is done by the car?
ANSWERS
2MJ
Kinetic Energy
Higher
Every moving body has Kinetic
Energy.
Kinetic Energy = mass (kg) x speed squared (m/s)2
2
Kinetic Energy =m x v2
2
Chapter 15
GCSE Additional Science
It is possible to calculate a moving
body’s kinetic energy by using:
For a diver weighing 70kg travelling at 54m/s………
Kinetic Energy = ½ × 70 × 542
= 102,060J = 102kJ
Chapter 15
GCSE Additional Science
Exemplar Questions
1) Megan drives her car at a speed of 30m/s.
If the total mass is 1000kg what is her
kinetic energy?
450kJ
2) Sioned’s speed on her bike is 10m/s. The
total mass of Sioned and her bike is 80kg,
so what is her kinetic energy?
4kJ
3) Dan runs with a kinetic energy of 750J. His
mass is 60kg; what’s his speed?
5m/s
4) Geraint walks to school. His kinetic energy
is 150J and his speed is 2m/s, so what is
his mass?
75kg
ANSWERS
Potential Energy
HIGHER
Potential energy is the energy that
every object has due to its position.
It is possible to calculate an object’s
potential energy by using:
(J)
(kg)
gravitational strength x height
(m/s2)
(m)
Potential Energy = mgh
Chapter 15
GCSE Additional Science
Potential Energy = mass x
For the book on top of the pile, it has a
mass of 0.7kg and it’s 2m from the floor,
so ………
Potential energy = 0.7 × 10 × 2 = 14J
Friction
1) What is friction?
2) Give 3 examples where friction can be a
problem.
4) What effect does friction have on surfaces?
Chapter 15
GCSE Additional Science
3) Give 3 examples where friction can be useful.
Braking Distances for a car…
A car’s braking distance is composed of two elements:
The thinking distance – this is the distance you travel whilst
reacting.
2)
Braking distance – this is the distance travelled whilst braking.
Braking
distance
14m
Total
23m
13m/s (30 m.p.h.)
38m
15m
53m
22m/s (50 m.p.h.)
21m
75m
31m/s (70 m.p.h.)
Chapter 15
GCSE Additional Science
Thinking
distance
9m
1)
96m
You do not need to learn the above figures for the
exam, but they show how the car’s speed affect its
stopping distance. What else affects a car’s stopping
distance?
A Car’s Stopping Distance …
High speed
Tiredness
GCSE Additional Science
Chapter 15
Drugs
Thinking
distance
Alcohol
Impaired
vision
Ice on the
road
Worn tyres or
brakes
Braking
distance
Wet road
surface
High speed
Car’s Stopping Distance
http://www.thinkroadsafety.gov.uk/me
diacentre/mediapage.htm
Chapter 15
GCSE Additional Science
Visit the website below to see video clips on the
effects of speed, tiredness, alcohol misuse etc.
on the stopping distance.