A car is moving with a uniform velocity of 30 m s-1. It is stopped in 2 s by applying a force of 1500 N through it’s brakes. Calculate (a) the change in momentum of car, (b) the retardation produced in car, and (c) the mass of the car.

Final velocity (v) = 0

Initial velocity (u) = 30 m s^-1

Time (t) = 2 s

Force (F) = 1500 N

Acceleration (a) = 0-30\over 2 = – 15 m s ^-2

Now,

Force (F) = mass (m) × acceleration (a)

⇒ 1500 = m × 15

⇒ m = 1500 / 15 = 100 kg

Initial momentum = mu = 100 × 30 = 3000 kg m s^-1

Final momentum = mv = 100 × 0 = 0

Substituting the values in the formula above we get,

Change in momentum = 0 – 3000 = – 3000 kg m s^-1

Hence,

(i) change in momentum = 3000 kg m s^-1

(ii) The retardation produced in the car = 15 m s ^-2

(iii) The mass of the car = 100 Kg