Question

A block of mass $10kg$ is connected to another block of mass $20kg$ 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 $200N$ starts acting on the block of mass $20kg$ to pull it. Find the force on the block of mass $10kg$ in $N$, if the acceleration of both blocks are same.

• A. $\frac{50}{3}$
• B. $\frac{100}{3}$
• C. $\frac{200}{3}$
• D. $\frac{400}{3}$

Answer 1

The correct option is C $\frac{200}{3}$

Using Newton's second law, acceleration of the whole system, $a=\frac{F_{\text{net}}}{M_{\text{total}}}=\frac{200}{10+20}$
$\Rightarrow$ Net force on block of mass ${}^{\prime }10k{g}^{\prime }=ma=\frac{10\times 200}{10+20}=\frac{200}{3}$