A force acting on an object of mass 500 g changes its speed from 200 cm/s to 0.2 m/s. The change in momentum is

Options

A. increase by 0.90 N s
B. decrease by 0.90 N s
C. increase by 90 g cm/s
D. decrease by 90 g cm/s

Answer

B

Explanation

Here , mass of the object, m = 500 g = 0 . 5 kg
Initial speed of the object , u = 200 cm/s = 2 m/s
Final speed of the object, v = 0 . 2 m/s
The initial momentum of the object is `p_(i) = m u = (0 . 5 kg) (2 m //s) = 1 kg m/s`
and the final momentum of the object is
`P_(f) = mv = (0 . 5 kg)(0 . 2 m//s) = 0 . 1 ` kg m/s
The change in momentum is
`Delta _(p) = p_(f) - p_(i) = (0 . 1 - 1) kg m//s = - 0 . 9 kg m//s = - 0 . 9 N s`
The negative sign shows decrease in momentum