Newton’s 3rd Law 11/27/13

Newton Hat Trick Video

Newton’s 3rd Law 11/24/14 (AP)

Newton’s 3rd Law 12/2/14

Background Information Newton’s Law of Universal Gravitation The Principia - Mathematical Principles of Natural Philosophy Newton’s three laws of motion is the foundation for his Universal Law of Gravitation

Newton’s Laws Quick Summary 1st Law: An object at rest stays at rest An object in motion stays in motion with the same velocity, if no net force 2nd Law: Accelerations are do to the net forces on an object (mass) 3rd Law: Action and reaction pair of forces

Newton’s 3rd Law (recap) Law III: To every action there is always an equal and opposite reaction: or the forces of two bodies on each other are always equal and are directed in opposite directions. When one body exerts a force on a second body, the second body exerts an equal and opposite force on the first. TWO objects and TWO forces Forces always come in pairs

Newton’s 3rd Law TWO Forces and TWO objects (TWO different F.B.D.) IF object A pushes/pulls on object B THEN object B pushes/pulls on object A in the opposite direction Object A push/pull – Action Force Object B push/pull – Reaction Force

Newton’s 3rd Law Examples The action force will be stated Identify the reaction force Draw the reaction force vector

Newton’s 3rd Law Examples Flower pulls on hand

Newton’s 3rd Law Examples Ball hits the bat

Newton’s 3rd Law Examples The Earth pulls on the skydiver. The skydiver pulls on the Earth.

Newton’s 3rd Law Examples Draw a F.B.D. of both objects and identify the action force and reaction force. Mr. Z. kicks a ball across to floor. What is the action force and reaction force? Action Force: Mr. Z. kicking the ball. Reaction Force: The ball pushing on Mr. Z.

Free Body Diagrams Mr. Z. Tennis Ball

Newton’s 3rd Law Examples One last example … This one is simple but a bit tricky!

Newton’s 3rd Law You (a student) sitting in a chair. Identify all action-reaction pairs Draw a free body diagram from each object Question: How many objects are involved in this situation? Three! You (the student), chair and the Earth Labeling the action-reaction pairs on the F.B.D.

Homework Newton’s 3rd Law Practice Due Tues. 11/25/14

Newton’s 3rd Law Examples You (a student) sitting in a chair. What are the action forces (two)? 1) The Earth pulling you down 2) You pushing on the chair These are both ACTION forces! What are the reaction forces? 1) You pulling on the Earth 2) The chair pushing on you

Free Body Diagrams

Homework Newton’s 3rd Law Practice Due Tues. 11/25/14