1. Using Motion Graphs (HT)
24 November, 2018
Using Motion Graphs (HT)
Objectives
Know how to use motion graphs to describe displacement, velocity and acceleration.
HSW: AF1 – Thinking scientifically
Used before in: lesson 3 – speed velocity acceleration
Will use again in:
PLTS: Team workers - collaborate with others to work towards common goals 
Keywords
Speed, Distance, Time, Seconds, Metres, metres/second, Distance-time, Displacement, Velocity, Gradient (slope), Uniform/constant/steady, stationery, area.

2. Outcomes All students should be able to:
Describe what the slope of distance – time and speed - time graphs means.
Recall the equation for acceleration.
Define displacement.
Most students should be able to:
Use displacement-time graphs to find velocity.
Use velocity-time graphs to find acceleration.
Some students should be able to:
Find the displacement travelled from a velocity-time graph.

3. Starter – What do we know?
What is speed?
What is velocity?
What is acceleration?
What do we find from the gradient of a distance-time graph?
What do we find from the gradient of a speed-time graph?
How can we find distance if we know speed and time?

4. Starter – What do we know?
What is speed? Distance/time
What is velocity? Speed in a direction
What is acceleration? (v-u)/t
What do we find from the gradient of a distance-time graph? speed
What do we find from the gradient of a speed-time graph? acceleration
How can we find distance if we know average speed and time? av speed x time

5. Speeding up (Accelerating) Slowing down (Decelerating)
Using graphs to describe motion
The slope, (gradient) of a distance – time graph shows speed
distance/m
speed/ m/s
Slow constant speed
Fast constant speed
time/s
time/s
distance/m
speed/ m/s
Speeding up
(Accelerating)
The slope, (gradient) of a speed – time graph shows acceleration
distance/m
time/s
speed/ m/s
time/s
Slowing down
(Decelerating)
time/s
time/s

6. Displacement is the distance travelled in a given direction.
Using graphs to describe motion
Displacement is the distance travelled in a given direction.
Velocity is the rate of change of displacement
Acceleration is the rate of change of velocity
This is a more precise definition because you do not have to change speed to change velocity – you could change direction!
The gradient of a displacement – time graph shows speed
displacement/m
velocity/ m/s
Fast constant speed
Slow constant speed
time/s
time/s
displacement/m
velocity/ m/s
Speeding up
(Accelerating)
The gradient of a velocity – time graph shows acceleration
time/s
displacement/m
velocity/ m/s
time/s
Slowing down
(Decelerating)
time/s
time/s

7. Motion
Displacement / Time Graph
D I S PLACEMENT / m
TIME / S

8. Motion Moving with a steady velocity.
D I S PLACEMENT / m
Moving with a steady velocity.
The gradient of the line tells you the velocity. y
Gradient = y x x
TIME / S

9. Motion Which line shows the movement of a fast object? A B TIME / S
D I S PLACEMENT / m A B
TIME / S

10. Motion What sort of motion does this line show? TIME / S
D I S PLACEMENT / m
TIME / S

11. Motion What sort of motion does this line show? TIME / S
D I S PLACEMENT / m
TIME / S

12. Motion What sort of motion does this line show? TIME / S
D I S PLACEMENT / m
TIME / S

13. Motion What sort of motion does this line show? TIME / S
D I S PLACEMENT / m
TIME / S

14. Motion
Velocity / Time Graph
V E L O C I T Y
m/s
TIME / S

15. Motion Moving with steady velocity V E L O C I T Y
Area under graph = total distance travelled
m/s
TIME / S

16. Motion Moving with steadily increasing velocity V E L O C I T Y
ACCELERATING
The gradient of the line tells you the acceleration. y x
m/s
Gradient = y x
TIME / S

17. Motion Moving with steadily increasing velocity V E L O C I T Y
ACCELERATING
Area under graph = total distance travelled
m/s
TIME / S
Area of a triangle
½ Time x Final Velocity
(This is the same as average velocity x time)

18. What is the speed during the first 20 seconds? 40 30 20 10
Distance
(metres)
Time/s
What is the speed during the first 20 seconds?
How far is the object from the start after 60 seconds?
What is the speed during the last 40 seconds?
When was the object travelling the fastest?
24/11/2018

19. 80 60 40 20
Velocity
m/s
T/s
How fast was the object going after 10 seconds?
What is the acceleration from 20 to 30 seconds?
What was the deceleration from 30 to 50s?
How far did the object travel altogether?
24/11/2018