New
New
Year 10
AQA
Foundation

# Calculating from velocity-time graphs (a = Δv/t)

I can read information from velocity-time graphs and calculate acceleration.

New
New
Year 10
AQA
Foundation

# Calculating from velocity-time graphs (a = Δv/t)

I can read information from velocity-time graphs and calculate acceleration.

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## Lesson details

### Key learning points

1. A velocity-time graph shows how velocity changes with time.
2. Acceleration is equal to the gradient of a velocity-time graph.
3. A falling line shows decreasing velocity called deceleration, which is a negative acceleration.

### Common misconception

Pupils often consider time in the acceleration equation to be moment in time (perhaps read from a graph) rather than a change in time.

Label the value of t in the acceleration as a change of time rather than just time.

### Keywords

• Displacement-time graph - A displacement-time graph shows the displacement of an object over a period of time.

• Velocity-time graph - A velocity-time graph shows the velocity of an object over a period of time.

• Acceleration - The acceleration of an object is the rate of change of velocity. This is how much the velocity changes per second.

• Deceleration - Deceleration is used to describe a change in velocity where the object slows down.

Emphasise use of the terms 'change in time' and 'change in velocity' throughout the lesson. Model acceleration and use video clips showing a range of changes in speed as examples.
Teacher tip

### Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

## Starter quiz

### 6 Questions

Q1.
Five yachts have a sailing race around the same course. Their completion times are shown. Starting with the fastest, put them in order of average speed.
1 - 1 hour 15 minutes
2 - 1 hour 19 minutes
3 - 1 hour 20 minutes
4 - 1 hour 28 minutes
5 - 1 hours 49 minutes
Q2.
An electric scooter has a maximum speed of 2.5 m/s. Calculate the maximum distance it can travel in 50 s.
2.5 m
20 m
47.5 m
52.5 m
Correct answer: 125 m
Q3.
Which word is used to describe an object which has a decreasing velocity?
Correct Answer: decelerating, deceleration
Q4.
Which of these is the correct unit for acceleration?
m
m/s
ms
m/s\$\$^3\$\$
Q5.
A satellite travels a distance of 10 800 km in 1 hour. What is the speed of the satellite in km/s?
10 800 km/s
180 km/s
Correct answer: 3.0 km/s
0.33 km/s
3.0 m/s
Q6.
A train speeds up from 2 m/s to 8 m/s in a time of 50 s. Calculate the acceleration of the train.
Correct answer: 0.12 m/s\$\$^2\$\$
0.16 m/s\$\$^2\$\$
0.04 m/s\$\$^2\$\$
8.3 m/s\$\$^2\$\$
6.0 m/s\$\$^2\$\$

## Exit quiz

### 6 Questions

Q1.
Match the key words and phrases to their explanations.
Correct Answer:displacement-time graph,this shows the displacement of an object over a period of time

this shows the displacement of an object over a period of time

Correct Answer:velocity-time graph,this shows the velocity of an object over a period of time

this shows the velocity of an object over a period of time

Correct Answer:acceleration,the rate of change of velocity

the rate of change of velocity

Correct Answer:deceleration,used to describe an object which is slowing down

used to describe an object which is slowing down

Q2.
Find the change in velocity between 0 s and 8 s shown in this graph.
2 m/s
Correct answer: -2 m/s
-8 m/s
8 m/s
6 m/s
Q3.
When is the magnitude (size) of the acceleration greatest according to the velocity-time graph?
between 0 s and 2 s
between 2 s and 4 s
between 4 s and 5 s
Correct answer: between 5 s and 7 s
between 7 s and 8 s
Q4.
The graph shows an electric car with changing velocity. At which of these times is the acceleration greatest?
Correct answer: 1 s
2 s
3 s
4 s
8 s
Q5.
The velocity-time graph shows the movement of a robotic arm in a factory. Calculate the velocity of the arm in m/s when the time is 10 s. You do not need to include the units in your answer.
Correct Answer: 0.15 m/s, 0.15
Q6.
A car starts from rest and accelerates at a constant 3.5 m/s\$\$^2\$\$. Calculate its velocity after 6.0 s.
Correct Answer: 21 m/s, 21.0 m/s, 21