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

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

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

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?

Distance-time graphs

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

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 60-100 seconds. 40 30 Distance/ m 20 10 20 40 60 80 100 Time/ s

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) 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

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

Speed-time graphs

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

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

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.

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

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.

Non-uniform acceleration 8 6 Time/s Speed/ m/s 4 2 30 60 90 120 150 Time/ s

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

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

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

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

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