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A 1000 kg car is travelling at 30 m/s. The brakes are applied until it stops. If the friction force between the tyres and the road is 5000 N, how long will the car take to come to rest?

1. 5 s
2. 10 s
3. 12 s
4. 6 s

Correct answer: 6 s

Solution

The car's deceleration can be calculated using Newton's second law, where the net force (friction) divided by mass gives the acceleration. With a friction force of 5000 N and a mass of 1000 kg, the deceleration is 5 m/s². Using the formula for time to stop (time = initial velocity / deceleration), we find that it takes 6 seconds for the car to come to rest.

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