Question

A rock is thrown 0.8 meters into the air. Find how fast it was thrown.

Answer 1

Answer:3.96 m/s

Explanation:

Given

Rock is thrown to a height of 0.8 m

We know that energy is conserved

Total Energy=kinetic Energy+Potential Energy

At bottom Kinetic Energy is maximum and Potential energy is minimum while at the top potential Energy is maximum and kinetic energy is minimum

Energy at Bottom $E_b=\frac{1}{2}mv^2+0$

Energy at Top $E_t=0+mgh$

Thus

$E_t=E_b$

$mgh=\frac{1}{2}mv^2$

$v=\sqrt{2gh}$

$v=\sqrt{2\times 9.8\times 0.8}$

$v=\sqrt{15.68}$

$v=3.96\ m/s$