give an example of a body that is in motion but that is also in equilibrium.?

Answer 1

water, be it sea, lake or even in a glass

Answer 2

The only possible motion an object in equilibrium is the uniform motion (motion in straight line with constant speed.). Example an aircraft (if a plane is moving -flying- but doesn't have equilibrium it will fall).
Other is the planet, they are in motion in their orbits but are in an equilibrium.