Mrs. Gergel Newton’s Third Law

For every action, there is an equal and opposite reaction.

Third Law of Motion When one object exerts a force on a second object, the second object exerts the same amount of force back on the first object but in the opposite direction.

Example If a student were to jump off of a desk onto the floor, their feet would sting. This is because the student’s feet would exert a force on the ground but the ground exerts a force back on the student’s feet, causing their feet to sting.

Example You jump on a trampoline and exert a downward force while the trampoline exerts an equal force upward, sending you high in the air.

3 rd Law Forces come in pairs – action and reaction Action: The hammer exerts a force on the nail Reaction: The nail exerts an equal and opposite force on the hammer.

Actions and Reactions Anytime something applies a force, there will be an equal and opposite force back in the opposite direction. Push on the handle of a lawnmower to make it go forward, and it will push back against you in the opposite direction with just as much force. This is the pressure that you feel of the handle against your hand. There is one ultra-important thing to remember when you are looking at action – reaction pairs. The two forces that you are looking at are each acting on different objects! If you are examining what you think are action-reaction forces, but the forces are both acting on the one object, it is not an action- reaction pair. In the above example, you exert a certain force on the lawnmower. The lawnmower exerts an equal force on you. Two objects, two forces.

Newton's Laws of Motion Newton ’ s Third Law: To every action, there is an equal and opposite reaction.

Newton ’ s 3 rd Law Example

Another Example of Newton ’ s 3 rd Law A Space Rocket! The engine pushes gases down. The rocket goes up.

Teacher Demo