A block of mass m is connected to another block of mass M by a spring (massless) of spring constant k. The block are kept on a smooth horizontal plane. Initially the blocks are at rest and the spring is unstretched. Then a constant force F starts acting on the block of mass M to pull it. Find the force of the block of mass M.

Options

A. `(MF)/((m+M))`
B. `(mF)/(M)`
C. `((M+m)F)/(m)`
D. `(mF)/((m+M))`

Answer

D

Explanation

Writing free body- diagrams for M & M we get,
`T=ma`
and F-T= Ma
where T is force due to spring
`rArr F-ma=Ma`
or, `F=Ma+ma`
`:. A=(F)/(M+m)`

Now, force acting on the block of mass M is
`ma=m((F)/(M+m))=(mF)/(m+M)`