A block of mass 'm' is connected to another block of mass 'M' by a spring (massless) of spring constant 'k'. The blocks 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 on the block of mass 'm'.

Options

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

Answer

b

Explanation

Here let a be the acceleration produced by the force F pulling the system, then if T is the force pulling the mass .m., we get
For the block of mass `M, F-T= Ma….(i)`

Also for the block of mass `m, T = ma…(ii)`
Adding (i) and (ii), `F = (M + m) a`
Or a`=(F)/(M+m)`
Putting in (ii) `T =(mF)/( M + m)`
Hence choice is (b).