Newton's’ Third Law of Motion Power Point

Newton's’ Third Law of Motion : 

Newton's’ Third Law of Motion By Ashley Clark Physics 101 December 1, 2010

What is Newton’s Third Law of Motion? : 

What is Newton’s Third Law of Motion? For every action, there is an equal and opposite reaction.

Slide 3: 

Click on the link below to watch a video that demonstrates Newton’s Third Law of Motion. http://www.schooltube.com/video/78539737ef62a43d9c34/Newtons-Third-Law-of-Motion

Check for Understanding… : 

Check for Understanding… 1. While driving down the road, a firefly strikes the windshield of a bus and makes a quite obvious mess in front of the face of the driver. This is a clear case of Newton's third law of motion. The firefly hit the bus and the bus hits the firefly. Which of the two forces is greater: the force on the firefly or the force on the bus?

Let’s see how you did! : 

Let’s see how you did! Trick Question! Each force is the same size. For every action, there is an equal ... (equal!). The fact that the firefly splatters only means that with its smaller mass, it is less able to withstand the larger acceleration resulting from the interaction. Besides, fireflies have guts and bug guts have a tendency to be splatterable. Windshields don't have guts. There you have it.

Check for Understanding… : 

Check for Understanding… 2. Many people are familiar with the fact that a rifle recoils when fired. This recoil is the result of action-reaction force pairs. A gunpowder explosion creates hot gases that expand outward allowing the rifle to push forward on the bullet. Consistent with Newton's third law of motion, the bullet pushes backwards upon the rifle. The acceleration of the recoiling rifle is ... a. greater than the acceleration of the bullet. b. smaller than the acceleration of the bullet. c. the same size as the acceleration of the bullet.

Let’s see how you did! : 

Let’s see how you did! The force on the rifle equals the force on the bullet. Yet, acceleration depends on both force and mass. The bullet has a greater acceleration due to the fact that it has a smaller mass. Remember: acceleration and mass are inversely proportional.

Check for Understanding… : 

Check for Understanding… 3. In the top picture (below), Kent is pulling upon a rope that is attached to a wall. In the bottom picture, the Kent is pulling upon a rope that is attached to an elephant. In each case, the force scale reads 500 Newton. Kent is pulling ... a. with more force when the rope is attached to the wall. b. with more force when the rope is attached to the elephant. c. the same force in each case.

Let’s see how you did! : 

Let’s see how you did! Kent is pulling with 500 N of force in each case. The rope transmits the force from Kent to the wall (or to the elephant) and vice versa. Since the force of Kent pulling on the wall and the wall pulling on Kent are action-reaction force pairs, they must have equal magnitudes. Inanimate objects such as walls can push and pull.

The End : 

The End