Year 9

iGCSE Physics

Relative Motion

Use the speed formula to answer the questions

1. A bottlenose dolphin detects an echo from a mackerel 50m away. The fish

detects the click and swims away at 5.5m/s, while the dolphin chases it at

9m/s.

a. Calculate the relative speed

b. How long will it take the dolphin to catch its dinner?

c. How far does each creature swim?

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2. Two cars are travelling in the same direction on a road. The slower car is

travelling at 23 m/s in front of the faster car, which is travelling at 32 m/s.

What is their relative speed?

3. A railway line and a road are side by side. A train and a car are travelling in

the same direction, with the train in front of the car. The train travels at 53

m/s and the car at 28 m/s. What is their relative speed?

4. Two cars are travelling on a road in opposite directions. The slower car is

travelling at 23 m/s and the faster car is travelling at 32 m/s. What is their

relative speed?

5. Explain why head-on collisions are much more dangerous than rear-end

collisions.

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For private use only. Not to be distributed without the express written permission of the publisher