(a) The momentum of a body is defined as the product of its mass and the velocity. It is a vector quantity and has direction same as the direction of velocity. From the definition of momentum, we can say that it depends on the mass and velocity of the body.
(b) Mass of the body = 5 kg
Initial velocity of the body = 20 m/s
The initial momentum of the body = 5 kg20 m/s = 100 kg m/s
Final velocity of the body = 0.20 m/s
Final momentum of the body = 5 kg0.20 m/s = 1 kg m/s
Change in momentum = 100 kg m/s - 1 kg m/s = 99 kg m/s
Hence, the change in momentum of the body is 99 kg m/s.