Question

The spring block system as shown in figure is in equilibrium. The string connecting blocks $A$ and $B$ is cut. The mass of all the three blocks is $m$ and spring constant of both the spring is $k$. The amplitude of resulting oscillation of block $A$ is

• A. $\frac{mg}{k}$
• B. $\frac{2mg}{k}$
• C. $\frac{3mg}{k}$
• D. $\frac{4mg}{k}$

Answer 1

The correct option is B $\frac{2mg}{k}$

Just after cutting the string, extension in spring = $\frac{3mg}{k}$
The extension in the spring when block is in mean position $=\frac{mg}{k}$
∴ Amplitude of oscillation
$A=\frac{3mg}{k}-\frac{mg}{k}=\frac{2mg}{k}$