Q. A ball of mass $2kg$ and another of mass $4kg$ are dropped together from a $60\ feet$ tall building. After a tall of $30\ feet$ each towards earth, their respective kinetic energies will be in the ratio of
A) $\sqrt{2}\ :1$
B) $1\ :4$
C) $1\ :2$
D) $1\ :\ \sqrt{2}$
Explanation
(c) Kinetic energy $= \frac{1}{2}mv^{2}$
As both balls are falling through same height therefore the possess same velocity
But $KE \propto m$ [If $v =$ constant]
$\therefore\frac{(KE)_{1}}{(KE)_{2}} = \frac{m_{1}}{m_{2}} = \frac{2}{4} = \frac{1}{2}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.