Question

A block of mass $m$ is connected to another block of mass $M$ by a massless spring 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. The force acting on the block of mass $m$ is

• A. $\frac{M F}{m+M}$
• B. $\frac{m F}{M}$
• C. $\frac{(M+m) F}{m}$
• D. $\frac{m F}{m+M}$

Answer 1

Answer: (D)

Acceleration of the system of two masses is
$a=\frac{F}{m+M}$
Force on the block of mass
$m=m a=\frac{m F}{m+M}$