Question

The body is thrown vertically upward at a speed of 20 m / s. At what height the kinetic energy of the body will be equal to its potential energy. Disregard air resistance

Answer 1

We have a condition for a certain height, where

$$PE=KE.$$

From conservation of energy, we have

$$KE_i=PE+KE,\\ KE_i=PE+PE=2PE.\\\space\\ \frac12mv^2=2·mgh,\\\space\\ h=\frac{v^2}{4g}=10.2\text{ m}.$$