Question

A ball of mass 1 kg is suspended by an inextensible string 1 m long attached to a point O of a smooth horizontal bar resting on fixed smooth supports A and B. The ball is released from rest from the mass of the bar is 4 kg. The displacement of bar when ball reaches the other extreme position (in m) is

• A. 0.4
• B. 0.2
• C. 0.25
• D. 0.5

Answer 1

Answer: (B)

0.2

Here,
Energy stored in pendulum = work done on block
$\therefore Mg\times s_p=mg\times s_b$
Displacement,
$s_b=x$
$s_p=2Lsin30=1$
Relative displacement,
$s_p=1-x$
Thus,
$M\left(x\right)=m(1-x)$
$4x=1-x$
$\therefore x=0.2$ m