Newton's first law: The motion of an object does not change unless an unbalanced force acts on it. Inertia is the tendency of matter to resist a change in motion and is proportional to the mass of an object. If an object is moving, it will keep moving in the same direction and at the same speed until an unbalanced force acts on it. An object that is not moving will continue to remain at rest until an unbalanced force causes a change in motion.

Newton's second law: When an unbalanced force acts on an object, the object will accelerate (speed up, slow down, change direction) in the direction of the applied unbalanced force. The acceleration will be proportional to the force and inversely proportional to the mass. A larger force will cause a greater acceleration and a larger mass will have a smaller acceleration. This relationship can be described mathematically using the formula force = mass x acceleration (F=ma).

Newton's third law: All forces come in pairs. For every force applied to an object, there exists simultaneously a force exerted by the object that is equal in magnitude and opposite in direction; these forces are applied to each of the objects in contact. For example, the force of the weight of an object on a table creates the simultaneous force of the table pushing up on the object; this is called the normal force. When a collision occurs between two objects, they each simultaneously exert an equal and opposite force on each other.