Newton's Third Law

Newton's Third Law of Motion

by: Alicia Heer

Isaac Newton was born on December 25, 1642 in Woolsthorpe, England. He attended the University of Cambridge in 1661. He is considered one of the greatest mathematicians and physicists of all time. He came up with some of the most popular theories of all time including the theory of gravity and the major laws of motion in physics.  He is known as the "Father of Science". 

Newton's three laws of motion explain why things move the way they do. 

Motion is defined as an act, process, or instance of changing place. Motion is any physical movement or change in position or place. 

• Newton's 1st Law of Motion - an object at rest stays at rest and an object in motion stays in motion unless acted on by an outside force .
• Newton's 2nd Law of Motion - if you apply a force to an object, it changes the objects speed .  force = mass times acceleration . 

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

In other words, if person 1 exerts a force on person 2, person 2 will exert the same magnitude of force on person 1, but in the opposite direction. These forces are called Action-Reaction Forces.

ACTION-REACTION FORCES:

• Equal and Opposite
• Always occur in pairs
• Occur at the SAME TIME!

Action-Reaction Force Example

Baseball pushes glove leftwards

      and

Glove pushes baseball rightwards

Action-Reaction Force Example

Bowling ball pushes pin leftwards

and

Pin pushes bowling ball rightwards

Can you name some Action-Reaction force pairs?

QUESTION?      

     While driving down the road, a bug hits the windshield of a bus. Quite obviously, this is a case of Newton's Third Law of Motion. The bug hits the bus and the windshield of the bus hits the bug. Which of the two forces is greater: the force on the bug or the force on the bus?

SO….if I push a chair, and then the chair falls over, is that an example of an action-reaction pair??