Calculating from motion graphs (a=Δv/t and v=s/t) | Physics

Starter quiz

Match the quantity to unit it is measured in.

mass

⇔

kilogram (kg) ✓

velocity

⇔

metres per second (m/s) ✓

displacement

⇔

metres (m) ✓

acceleration

⇔

metres per second squared (m/s $^2$ ) ✓

time

⇔

seconds (s) ✓
What is the velocity of this object at time of 3 s?

1 m/s

3 m/s

5 m/s

6 m/s ✓

9 m/s
Which of these is a correct definition of acceleration?

The rate of change of velocity ✓

The rate of change of displacement

The rate of change of speed

The overall change in velocity

The overall change in position
During which time period is this object decelerating?

Between 0 s and 2 s.

Between 2 s and 4 s.

Between 4 s and 5 s.

Between 5 s and 7 s. ✓

Between 7 s and 8 s.
A speedboat increases in velocity from 2.0 m/s to 14 m/s in a time of 8.0 s. Calculate the acceleration of the speedboat.

0.25 m/s $^2$

0.67 m/s $^2$

1.5 m/s $^2$ ✓

1.75 m/s $^2$

12 m/s $^2$
The displacement-time graph shows the movement of a robot. Calculate the velocity of the robot at time = 45 s.

'-0.1 m/s' ✓

Match the key words and phrases to their explanations.

displacement-time graph

⇔

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

velocity-time graph

⇔

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

acceleration

⇔

the rate of change of velocity ✓

velocity

⇔

the rate of change of displacement ✓
The graph shows the movement of a van over time. Find the total distance travelled for the journey.

20 km

30 km

50 km

70 km

100 km ✓
The graph shows the movement of a van making two deliveries. Find the average speed of the van during the outwards journey, from 0 to 3 hours.

17 km/h ✓

17 m/s

10 km/h

10 m/s

0.6 km/h
The graph shows the displacement of a dynamics trolley along a bench. Calculate the velocity of the trolley at time = 2 s.

0.20 m/s ✓

0.27 m/s

0.16 m/s

0.40 m/s

5.0 m/s
Find the distance travelled by this object during the first 2 seconds of motion.

1 m

2 m

4 m

8 m ✓

16 m
Use the graph to find the acceleration of the moving object between time = 2 s and time = 4 s.

0.25 m/s $^2$

0.50 m/s $^2$

0.75 m/s $^2$

1.5 m/s $^2$

2.0 m/s $^2$ ✓

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A displacement–time graph shows how displacement changes with time.
A velocity–time graph shows how velocity changes with time.
Displacement–time and velocity–time graphs of the same motion have different shapes.
Acceleration is equal to the gradient of a velocity–time graph.
A falling line shows deceleration (decreasing velocity) which is a negative acceleration.

Pupils often confuse displacement–time graphs with velocity–time graphs.

Emphasise the need for pupils to always read the axes of a graph first, before they start to think about any lines drawn on it.

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.
Velocity - The velocity of an object is the rate of change of displacement. This is how fast it is moving in a particular direction.
Acceleration - The acceleration of an object is the rate of change of velocity. This is how much the velocity changes per second.