What keeps the planets in orbit around the sun?

What is the weight of a feather (mass = 0.0001 kg) that floats through earth's and the moon's atmospheres?

This energy transformation diagram represents the energy of a skateboarder moving along a half-pipe. as she skates toward the top of the half-pipe, her original kinetic energy is converted to potential energy and friction. how much of the energy is potential?

In which of the following is positive work done by a person on a suitcase