Calculate the potential energy of 5.0g (0.005 kg) paper airplane 5.0 meters above the ground

How would a small bar magnet be oriented when placed at position x?

You throw a small rock straight up from the edge of a highway bridge that crosses a river. the rock passes you on its way down, 7.00 s after it was thrown. what is the speed of the rock just before it reaches the water 28.0 m below the point where the rock left your hand? ignore air resistance.

What is the single most important equation in all of physics?