After falling from rest through a height `h`, a body of mass `m` begins to raise a body of mass `M (M gt m)` connected to it through a pulley.
Find the fraction of kinetic energy lost when the body of mass `M` is jerked into motion

Options

A. `M/(M+m)`
B. `M/(M-m)`
C. `(2M)/(M+m)`
D. `M/(2(M+m))`

Answer

A

Explanation

Fraction of `KE` lost`=(1/2"mu"^(2)-1/2(M+m)v^(2))/(1/2"mu"^2)`
`=1-(M+m)/m (v/u)^(2)=1-(M+m)/m(m/(M+m))^(2)=m/(M+m)`