Q. A plate of mass $m$, length $b$ and breadth $a$ is initially lying on a horizontal floor with length parallel to the floor and breadth perpendicular to the floor. The work done to erect it on its breadth is
A) $mg\left\lbrack \frac{b}{2} \right\rbrack$
B) $mg\left\lbrack a + \frac{b}{2} \right\rbrack$
C) $mg\left\lbrack \frac{b - a}{2} \right\rbrack$
D) $mg\left\lbrack \frac{b + a}{2} \right\rbrack$
Explanation
(c) Initial height of CG$= \ \frac{a}{2}$
Final height of CG $= \ \frac{b}{2}$
Work done$= mg\ \left\lbrack \frac{b}{2} - \frac{a}{2} \right\rbrack = mg\left( \frac{b - a}{2} \right)$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.