Question

1. A car is moving with a uniform velocity 30 m s-1. It is stopped in 2 s by applying a force of 1500 N through its brakes. Calculate : (a) the change in momentum of car, (b) the retardation produced in car, and (c) the mass of car. Ans. (a) 3000 kg m s-1 (b) 15 m s-2 (c) 100 kg​

Answer 1

Answer

Initial velocity , u = 30m/s

Force = 1500 N

Time , t = 2 sec

To find :

The change in momentum and the retardation in car .

Solution :

Using the first equation of motion ,

v = u - at

where , v is final velocity ,

minus sign for retardation .

putting the values ,

0 = 30 - a * 2

a = 15 m/s^{2}s

2

now,

force = 1500 N

m * a = 1500 N

m = 100 kg

change in momentum of car = m ( v - u )

= 100 (-30)

= - 3000 kg m /s

The reatardation is 15m/s^{2}s

2

and the change in momentum is - 3000 kg m /s .