Question

A ball of mass $2 \,kg$ and another of mass $4\, kg$ are dropped together from a $60$ feet tall building. After a fall 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. $1 : \sqrt 2$

Answer 1

Answer: (C)

$1 : 2$

Answer 2

Here $V _{1}= V _{2}=\sqrt{2 gh }$
$\frac{ KE _{1}}{ KE _{2}}=\frac{\frac{1}{2} m _{1} v _{1}^{2}}{\frac{1}{2} m _{2} v _{2}^{2}}$
$=\frac{ m _{1}}{ m _{2}}=\frac{2}{4}=\frac{1}{2}$