Q. 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) $\frac{M + m}{m}l$
Explanation
(b) If the both mass are revolving about the axis $yy'$ and tension in both the threads are equal then
$M\omega^{2}x = m\omega^{2}(l - x)$
$\Rightarrow Mx = m(l - x)$
$\Rightarrow x = \frac{ml}{M + m}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.