1. Syllabus Statements Speed, velocity and acceleration
• Define speed and calculate speed from total time total distance
• Plot and interpret a speed/time graph or a distance/time graph
• Recognise from the shape of a speed/time graph when a body is
a. – at rest
b. – moving with constant speed
c. – moving with changing speed
4. • Calculate the area under a speed/time
graph to workout the distance travelled
for motion with constant acceleration
• Demonstrate some understanding that
acceleration is related to changing speed
• Distinguish between speed and velocity
• Recognise linear motion for which the acceleration is constant and calculate the acceleration
• Recognise motion for which the acceleration is not constant

2. Objectives Define speed
To get a C you need to be able to…
Define speed
To get a B you need to be able to…
Can accurately calculate the distance using a speed time graph.
To get a A/A* you need to be able to…
Can Calculate the acceleration using a Speed time graph and give the correct units

3. Definitions Distance Displacement Speed Velocity Acceleration
Change in velocity
time
Distance
Displacement
Speed
Velocity
Acceleration
Distance
time
Displacement
time
Distance × time
Length from the starting position to the end position in a known direction
“as the crow flies”
Kinetic energy gained in 1 second
Total length of the path travelled
Length of the path travelled in one second

4. Definition of speed 3 quick calculations
I take 12.6 seconds to complete a 100m race, what is my speed?
I am (slightly) worse at 200m with a speed of 7.8m/s, how long does it take me to finish?
The speed of a motorbike is 30mph (13.4m/s) and travels for 45minutes, what is the distance travelled?

5. Distance-time graphs

6. Distance/ m Time/ s How far had the object gone after 20 seconds?
When is the object staying still?
What can you say about the steepness of the line and the value of
the gradient. 40 30
Distance/ m 20 10 20 40 60 80
100
Time/ s

7. 5) Calculate the gradient of the line between 0 and 20 seconds
6) What are the units of this value? (Use the units on the graph)
Calculate the gradient for 40 – 60 and seconds. 40 30
Distance/ m 20 10 20 40 60 80
100
Time/ s

8. 8) Sketch the speed time graph for the motion from the previous graph
i) Set the time axis to be the same as before
ii) Label your speed axis, think carefully about the scale…
iii) Plot the graph, it will look odd, remember you are allowed to do
“dot to dot”
Time/s

9. 9) Why does this graph look so odd
9) Why does this graph look so odd? Think what is happening between each change of speed.
2.0
1.0
Speed/ m/s
0.0 20 40 60 80
100
Time/ s
-1.0
-2.0

10. Distance/ m Time/ s EXTENSION- Comparing Distance time graphs
Who got away quickest?
Who had the fastest maximum speed?
What happened at 5 seconds?
Who won the race?
100 75
Distance/ m 50 25 2 4 6 8 10
Time/ s

11. Speed-time graphs

12. Time/s Speed/ m/s Time/ s When is the object travelling at 4m/s ?
What does the area under the graph represent? (think of the axis)
Calculate the area underneath the graph. (you may want to split it up into rectangles and triangles) 8 6
Time/s
Speed/ m/s 4 2 10 20 30 40 50
Time/ s

13. Time/s Speed/ m/s Time/ s
4) What does the gradient of the line represent in this graph? (think of the axis)
5) Calculate the gradient between 0 and 20 seconds.
6) What is happening between 40 and 50 seconds? 8 6
Time/s
Speed/ m/s 4 2 10 20 30 40 50
Time/ s

14. Uniform acceleration
On a speed-time graph a straight slopped line represents uniform acceleration. This would be seen as a curve on a distance time graph.

15. Speed/ m/s Time/ s Distance/ m Time/ s 8 6 4 2 10 20 30 40 50 200 15010 20 30 40 50
Time/ s
200
150
Distance/ m
100 50 10 20 30 40 50
Time/ s

16. Non-uniform acceleration
If you have a curved line on a speed-time graph this represents non-uniform acceleration. You only need to be able to recognise this. In your books write a sentence saying what graph 5 represents.

17. Non-uniform acceleration8 6
Time/s
Speed/ m/s 4 2 30 60 90
120
150
Time/ s

18. EXTENSION- Speed time graphs with non uniform acceleration
Calculate the distance travelled for this journey?
- is it an overestimate or an underestimate?
Explain why this journey better represents a real journey than the other graphs we have looked at. 20 15
Speed/ m/s 10 5 10 20 30 40 50
Time/ s

19. Objectives Define speed
To get a C you need to be able to…
Define speed
To get a B you need to be able to…
Can accurately calculate the distance using a speed time graph.
To get a A/A* you need to be able to…
Can Calculate the acceleration using a Speed time graph and give the correct units

20. Deceleration Constant speed Faster constant speed Slowing down
Uniform Acceleration
Deceleration
Constant speed
Faster constant speed
Slowing down
Stationary 40 30 E
Distance/ m F 20 D 10 C B A 20 40 60 80
100
Time/ s

21. Stationary Constant speed Deceleration Faster constant speed
Uniform Acceleration
Faster constant speed
Slowing down 40 30 E
Speed/ m/s F 20 D 10 C B A 20 40 60 80
100
Time/ s

22. Syllabus Statements Speed, velocity and acceleration
• Define speed and calculate speed from total time total distance
• Plot and interpret a speed/time graph or a distance/time graph
• Recognise from the shape of a speed/time graph when a body is
a. – at rest
b. – moving with constant speed
c. – moving with changing speed
4. • Calculate the area under a speed/time
graph to workout the distance travelled
for motion with constant acceleration
• Demonstrate some understanding that
acceleration is related to changing speed
• Distinguish between speed and velocity
• Recognise linear motion for which the acceleration is constant and calculate the acceleration
• Recognise motion for which the acceleration is not constant