Transcript Describing Motion PowerPoint

Chapter 2: Motion
 Compare your maximum speed with
that of a cheetah, horse, elephant,
and snake. Could you win a race
against any of them?
 Distinguish between distance and
displacement.
 Explain the difference between
speed and velocity.
 Interpret motion graphs.
 A reference point is needed to
determine the position of an object.
 Motion occurs when an object changes
position relative to its reference point.
 Distance: how far an object has moved
 Displacement: the distance and
direction of an object’s change in
position from the starting point
 The SI unit for distance and displacement
is the meter (m).
A runner runs from the start
line 50 m north plus 30 m in
the opposite direction.
What is the distance?
What is the displacement?
40 meters
22 meters
22 meters
40 meters
 Speed: the
distance an
object travels
per unit of
time
 Speed = distance / time
 Speed = d/t
 Distance measured in meters (m)
 Time measured in seconds (s)
 Speed measured in meters/seconds (m/s) or
kilometers/hour (km/h)
 Speed = d/t
 Distance =
 Time =

A car traveling at a constant speed covers a
distance of 750 m in 25 s. What is the car’s
speed?

A man runs at a speed of 2.30 m/s. How long
does it take for the man to run 50 m?

A car is travelling at 30 km/hr for 125 s. How
far does the car travel in meters?
 Average speed: total distance
traveled divided by the total time of
travel
 Instantaneous speed: speed at a
given point in time
40 meters
4s
22 meters
11 s
2s
10 s
40 meters
22 meters

Motion can be
shown on a distance
vs. time graph
 Time on x-axis
 Distance on y-axis

On a distance vs. time
graph the slope
describes the speed
 Steeper slope = faster
speed
 Horizontal line = zero
speed = object at rest
Distance
(m)
Time (s)

Velocity: includes the speed of an object
and the direction of its motion

Because velocity depends on direction as
well as speed, the velocity of an object can
change even when its speed does not!
Car is driving 30
km/hr, but its velocity
is constantly
changing!
40 meters
4s
22 meters
11 s
2s
10 s
40 meters
22 meters
 Miss Marnik walked a distance of
1.60 km in 30 min. Find her average
speed in m/s.