Rover was thrown from his owner's airplane after the owner discovered that Rover was no "plane broken" (house broken or the plane.) Luckily, Rover thought to wear his parachute on the plane. He opened it immediately as her was hurled out of the door. After several seconds, Rover had drifted to a position of 200 meters above the ground. Compute (if possible) his potential energy at this location above the ground. Rover has a mass of 4 kg. Explain your answer.

The potential energy that Rover has depends on his mass m and his height over the ground, h. The formula for potential energy is E = mgh, where g = 9.81 m/s^2 is the gravity acceleration. So,

E = mgh = 4 kg * 9.81 m/s^2 * 200 m = 7848 J (joules). However, we need to round off the result up to a single significant figure because the measured data (4 kg) has only 1 significant figure.