A 30-N iPad is dropped from a height of 10 m and strikes the ground with a speed of 13 m/s. What average force of air friction acted on the iPad as it fell?
expected impact energy ... m * g * h = 30 * 9.8 * 10
actual impact energy ... 1/2 * m * v^2 = 1/2 * 10 * 13^2
the difference in the energies is the work done by air friction
... w = force * distance = 10 f