Question

what will be the magnitude of change in momentum imported by the fluid to A ball of mass 1 Kg if it falls from a height of 100m on the fluid and reward vertically upward with same speed

Answer 1

Given
Height = 100m
mass = 1kg

As momentum = Mass × velocity

Then velocity just before touching fluid
v^2 = u^2 + 2gs
or
v^2 = 198
or
v = 14.1 m/s

now as rebound velocity = falling velocity

then
momentum 1 = 1 × 14.1 kg m/s
= 14.1 kg m/s
momentum 2 = 1× - 14.1 kg m/s
= - 14.1 kg m/s
now
change in momentum
= momentum1 -momentum2

= 14.1 - 14.1

= 28.2 kg m/s

hope it helps