Question

Two masses M and m are attached to a vertical axis by weightless threads of combined length l. They are set in rotational motion in a horizontal plane about this axis with constant angular velocity $\omega$. If the tensions in the threads are the same during motion, the distance of M from the axis is

• A. $\frac{Ml}{M+m}$
• B. $\frac{ml}{M+m}$
• C. $\frac{M+m}{M}l$
• D. $\frac{M+m}{m}l$

Answer 1

The correct option is B

$\frac{ml}{M+m}$

If the both mass are revolving about the axis yy' and tension in both the threads are equal then
$M{\omega }^{2}x=m{\omega }^2(1-x)$
$\Rightarrow Mx=m(l-x)$
$\Rightarrow x=\frac{ml}{M+m}$