Question

A car is moving with a uniform velocity 30 ms^-1. It is stopped in 2 s by applying a force of 1500 N through its brakes. Calculate the following values : The change in momentum of car.

Answer 1

Initial velocity, u = 30 m/s

Final velocity, v = 0

Time, t = 2s

Force, F = 1500 N

Here, a = (v - u)/t = (0 - 30)/ 2 = - 15 ms^-2. Here, negative sign indicates retardation.

Now, F = ma.

Or, m = F/a = (1500/ 15) = 100 kg.

Change in momentum = Final momentum - Initial momentum

Or, Δp = m (v - u)

Or, Δp = 100 (0 - 30)

Or, Δp = 3000 kg m/s^-1