Conservation of Energy

A ball falls from rest through 5.0 m. Find its speed.

A 2.0 kg object falls from rest through 8.0 m. It reaches 10 m s⁻¹. Calculate the energy dissipated by air resistance.

Worked answer: GPE lost = $2.0\times9.81\times8.0=157\text{ J}$. KE gained = $\tfrac12(2.0)(10)^2=100\text{ J}$. Energy dissipated = $157-100=57\text{ J}$.