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 accelerate it. Find the force on the block of mass $m$.

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

Answer 1

The correct option is D $\frac{mF}{m+M}$

Using Newton's second law, acceleration of the whole system, $a=\frac{F_{\text{net}}}{M_{\text{total}}}=\frac{F}{m+M}$
$\Rightarrow$ Net force on block of mass ${}^{\prime }{m}^{\prime }=ma=\frac{mF}{m+M}$