Question

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

Answer 1

Initial velocity, u = 30 m/s

Final velocity, v = 0

Time, t = 2s

Force, F = 1500 N

F = `(Δp)/(Δt)`

1500 = `(Δp)/2`

Δp = 3000 kg m/s 

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