A metal ball dropped from a height has $50$ J of gravitational potential energy at the start. Halfway down…
A metal ball dropped from a height has $50$ J of gravitational potential energy at the start. Halfway down its fall, its measured kinetic energy is $25$ J. Assuming air resistance is negligible, what is its potential energy at this halfway point?
$50$ J
$25$ J
$0$ J
$75$ J
Solution
Total energy is conserved ($50\text{ J}$). At halfway, $\text{Total Energy} = \text{Potential Energy} + \text{Kinetic Energy}$. So $\text{Potential Energy} = 50\text{ J} - 25\text{ J} = 25\text{ J}$.