Question

A 1.0-kg ball falls to the floor. When it is 0.90 m above the floor, its potential energy exactly equals its kinetic energy. How fast is it moving

Answer 1

$\text{Given that,}\\\\\text{Mass, m = 1 kg and height, h = 0.90 m}\\\\\text{Acoording to the condition,}\\\\mgh = \dfrac 12 mv^2\\\\\implies g h = \dfrac{v^2}2\\\\\implies v^2 =2gh\\\\\implies v = \sqrt{2gh} = \sqrt{2 \times 9.81 \times 0.90} = \sqrt{17.658} = 4.203 ~ \text{ms}^{-1}$