Question

A ball is falling freely from a height. When it reaches $10\, m$ height from the ground its velocity is $v_{0}$. It collides with the ground and loses $50 \%$ of its energy and rises back to height of $10\, m$. Then the velocity $v_{0}$ is

• A. 7 m / s
• B. 10 m / s
• C. 14 m / s
• D. 16 m / s

Answer 1

Answer: (C)

At height $10\, m$, the kinetic energy equal to potential energy then
$\frac{1}{2} mv_{0}^{2}=mgh$
$\frac{1}{2} v_{0}^{2} =9.8 \times 10$
$v_{0}^{2} =2 \times 9.8 \times 10$
$v_{0} =\sqrt{196}$
$v_{0} =14\, m / s$