1. Speed, velocity and acceleration

2. Core Define speed and calculate speed from Total distance/total time
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
– at rest
– moving with constant speed
– moving with changing speed
Calculate the area under a speed/time graph to work out the distance travelled for motion with constant acceleration
Demonstrate some understanding that acceleration is related to changing speed

3. Supplement
Distinguish between speed and velocity

4. You will learn How to calculate average speed
The difference between speed and velocity
How to calculate acceleration
How to interpret velocity-time graphs.

5. Speed and velocity Speed is a _______________ quantity.
Speed is measured in __________ (units).
The average speed of an object can be calculated using the equation:
Instantaneous speed is more difficult to measure but can be found by looking at the _________________ of a _____________ vs . time graph.

6. Velocity
Velocity is a _______________ quantity it has both magnitude and _________________.
Velocity is measured in __________ (units).
Hence a change in _____________ causes a change in velocity.
E.g. 1 A car going at a constant ___________ in a circle has a changing velocity.
E.g. 2 An object travelling at 10m/s that returns to its original position has an average velocity of ___ m/s.

7. Acceleration Acceleration is a _______________ quantity.
Acceleration is measured in __________ (units).
The Acceleration of an object can be calculated using the equation: Acceleration = __________
Acceleration can be found by looking at the _________________ of a _____________ vs . time graph.
A negative Acceleration is called ___________

8. Activities
Read p 26+27
Answer questions on page 27

9. Velocity time graphs

10. Velocity time graphs.
Velocity – time graphs can show information about the motion of an object in more ________
The _____________ of the line on a v-t graph tells us about the acceleration.
A greater acceleration is shown by a _________ line.
If acceleration is constant the line is _________
An increasing acceleration is shown by a line that _____________ _____
A decreasing acceleration is shown by a line that _____________ _____
The distance travelled by an object can be determined by the __________ ________ _______ ________

11. To do
P29 q 2

12. Experiment

13. Supplement
Recognise linear motion for which the acceleration is constant and calculate the acceleration
Recognise motion for which the acceleration is not constant

14. You will learn
How to recognise constant acceleration on a speed-time graph
How to calculate acceleration from a speed – time graph
How to recognise non constant acceleration from a speed time graph

15. Practice
P35 q 1&2

16. v = at when applied to an object accelerating uniformly from rest
What is the equation for acceleration?
acceleration = Change in velocity / time
So Change in velocity = ?
acceleration x time
Change in velocity = ?
Final velocity – initial velocity (v-u)
What if initial velocity is zero?
v = at

17. Summary questions
A car accelerates from 10 m/s to 25 m/s over a period of 5 seconds. What is the acceleration?
2. A wombat falls out of a tree into a vat of custard. It starts from rest, and accelerates at 10 m/s2 until it lands in the custard 5 seconds later. How fast is it going when it hits the custard?

18. Chapter 18 : Velocity and Acceleration 1
Answers
Chapter 18 : Velocity and Acceleration 1
A car accelerates from 10 m/s to 25 m/s over a period of 5 seconds. What is the acceleration?
2. A wombat falls out of a tree into a vat of custard. It starts from rest, and accelerates at 10 m/s2 until it lands in the custard 3 seconds later. How fast is it going when it hits the custard?
Acceleration = (change in velocity) ÷ time
= (25 – 10) ÷ 5
= (15) ÷ = 3 m/s2
Acceleration = (change in velocity) ÷ time
10 = (v – 0) ÷ 3
So v = 3 × = 30 m/s That’s over 60 mph – ouch!

19. Velocity and Acceleration
Use these words to label the graphs correctly.
stopped
slow
fast
fast
stopped
accelerating
decelerating

20. Velocity and Acceleration
Answers
Velocity and Acceleration
Use these words to label the graphs correctly.
stopped
slow
fast
fast
stopped
accelerating
decelerating
accelerating
decelerating
fast
stopped
fast
stopped
slow