Q. A man of $50\ kg$ mass is standing in a gravity free space at a height of $10m$ above the floor. He throws a stone of $0.5\ kg$ mass downwards with a speed of $2m/s$. When the stone reaches the floor, the distance of the man above the floor will be
A) $20m$
B) $9.9m$
C) $10.1m$
D) $10m$
Explanation
(c) Let distance of man from the floor be $(10 + x)m$. As centre of mass of system remains at $10m$ above the floor
So $50(x) = 0.5(10) \Rightarrow x = 0.1m$
$\Rightarrow$ distance of the man above the floor $= 10 + 0.1$
$= 10.1m$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.