Question

A small ball B of mass m is suspended with light inelastic string of length L from a block A of same mass m which can move on smooth horizontal surface as shown in the figure. The ball is displaced by angle $\theta $ from equilibrium position & then released.

The displacement of block when ball reaches the equilibrium position is

• A. $\frac{\text{L sin } \theta }{2}$
• B. $\text{L sin } \theta $
• C. L
• D. None of these

Answer 1

Answer: (A)

$\Delta \text{x}_{\text{cm}} = 0$
$0 = - \left(\text{L sin} \theta - \text{x}\right) \text{m} + \text{mx}$
$\text{L sin} \theta - \text{x} = \text{x}$
$2 \text{x} = \text{L sin} \theta $
$\text{x} = \left(\text{L sin} \theta \right) / 2$