Have you ever wondered what happens to an object moving in one direction?
First, if an object is moving in one direction it's eventually going to stop because of friction. Also if it's moving in the air it going to drop/fall to Earths surface. That happens because of the powerful force of gravity. Last, sometime soon it's going to change direction left, right, up or down. Maybe because someone adds force to an object. If it is wasn't for gravity or forces of motion many things will not be able to move in one direction