Question

What is the kinetic energy of a 150 kg rock thrown 75 m/s?

Answer 1

The relation between the mass, velocity and kinetic energy is,

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

where m is the mass of the rock, v is the velocity.

Substituting the known values,

$\begin{gathered} K=\frac{1}{2}\times150\times75^2 \\ K=421875 \\ K=421.9\text{ kJ} \end{gathered}$

Thus, the kinetic energy of the rock is 421.9 kJ.