Question

A car is moving with a velocity of 10 m/s. The force applied by the brakes will be maximum if the time taken by the car to come to rest is:

• A. 12 seconds
• B. 10 seconds
• C. 5 seconds
• D. 20 seconds

Answer 1

The correct option is C 5 seconds

Force is directly proportional to the rate of change of momentum.
As, the rate of change of momentum is given by $\frac{mv-mu}{t}$, it will be highest when the time taken is minimum.
Consequently, force will be maximum when the time taken is minimum.
Therefore, the force applied by the brakes will be maximum when the time taken by the car to come to rest is 5 seconds.