The world is filled with motion. Some motions just happen: the Earth revolves around the Sun, snowflakes fall to the ground, waves surge across the sea. Other motions are under our control. We walk. We pick up things. We ride our bikes. But whether the movement is a planet revolving or you playing a game, the motion happens because of force.

Just what is Force? Force is just a fancy word for pushing or pulling. If I push on something or pull on it, then I am applying a force to it. Forces make things move or, more accurately, make things change their motion. Two natural forces that affect most of the motion we are aware of are the force of gravity and electromagnetic forces. Gravity produces a force that pulls objects towards each other, like a person towards the ground. And magnetism produces a force that can either pull two magnets together or push them apart, depending on how they’re lined up. What is Friction? Friction is a force that makes the objects move together or at least have more nearly the same velocity. Say you were pushing a toy train across the floor. It doesn't take much effort or force, because the toy is light. Now say you try to push a real train. You probably can't do it because the force of friction between the train and the ground. The heavier the object, the stronger the force of friction. What is Gravity? Gravity produces a force that pulls objects toward one another. It is the force that keeps the Earth revolving around the sun and it's what pulls you to the ground when you trip. Newton’s laws of Motion Some consider Sir Isaac Newton to be the greatest English mathematician of his time and perhaps one of the greatest scientists the world has known. According to a story, Newton saw an apple fall to the ground and he figured out that the same force which caused the apple to fall also governed the motion of the Moon and the planets. In 1687 Newton published his three laws of motion in the "Principia Mathematical Philosophies Naturalism”. His three laws explained how the concepts of force and motion work.