Question

A ball of mass $2kg$ and another of mass $4kg$ are dropped together from a $60ft$ tall building. After a fall of $30ft$ each towards earth, their respective kinetic energies will be in the ratio of

• A. $1:\sqrt{2}$
• B. $\sqrt{2}:1$
• C. $1:4$
• D. $1:2$

Answer 1

Answer: (D)

Since travelling distance is same for both balls, their velocities at the end of 30 feet journey will be same
$\therefore \frac{K . E_{1}}{K . E_{2}}=\frac{\frac{1}{2} m_{1} v_{0}^{2}}{\frac{1}{2} m_{2} v_{0}^{2}}=\frac{m_{1}}{m_{2}}=\frac{2}{4}=\frac{1}{2}$
$ \, $