The masses of `10kig` and `20kg` respectively are connected by a massless spring as shown in figure. A force of `200N` acts on the `20kg` mass. At the instant shown, the `10kg` mass has acceleration `12m//sec^(2)` . What is the acceleration of `20kg` mass?

Options

A. `12m//sec^(2)`
B. `4m//sec^(2)`
C. `10m//sec^(2)`
D. Zero

Answer

B

Explanation

As the mass of `10kg` has acceleration `12m//s^(2)` therefore it apply `120N` force on mass `20kg` in a backward direction.
:. Net forward force on `20kg` mass
`=200-120=80N`
:. acceleration of the block is `=(4kx)/(m)` .