Question

Calculate the work required to be done to stop a car of 1500 kg moving at a velocity of 60 km/h?

Answer 1

Here, the mass of the car, m = 1500 kg

The initial velocity of the car, u = 60 km h^-1

= `(60 xx 1000  m)/(60 xx 60  s)`

= `50/3  ms^-1`

The initial kinetic energy of the car,

`K.E_i = 1/2 "mu"^2`

= `1/2 (1500  kg) (50/3  ms^-1)^2`

= 208333.3 J

Final kinetic energy of the car,

`K.E_f = 1/2 mv^2`

= 0

Change in kinetic energy of the car

= K.E_f - K.E_i

= - 208333.3 J

The minus sign indicates the work is being done against the moving car.