ch6_pswc



Chapter 6- Newtons third law of motion. Action and Reaction.

The first thing that it deals with is the pushing and pulling of object. it is called forces and interactions.


 * **__Interaction__** - causes there to be a pair of forces.
 * If a hammer hits a nail the nail in return will produce a force . [[image:IsaacNewton.gif width="94" height="91"]]
 * it will also push back on the hammer.

__Newton’s third law__ - whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first object.
 * __Action force__**- the force that is applying the force initially
 * __Reaction force__**- is the force that is applied to the object that hit the object initially.

Identifying action and reactions

Identifying actions are very easy to see and figure out, but reaction forces are not that easy, whatever the action force is, the reaction force always involves the same two objects. example - Action the earths gravity pulling you down reaction you being pulled up with the same force.

These two forces have to be in contact to interact.

 Action and reaction on different masses

Action and Reaction forces always act on a pair of objects. When a gun is fired the action is the gun acting on the bullet, the reaction is the bullet pushing back on the gun. the bullet will have a larger acceleration because the bullet has such a small mass and the gun has a much larger mass.

Action and Reaction forces can __ **never** __ cancel each other.

Action equals Reaction

To apply a force to a object that object must be able to apply equal and opposite force to that object. - The example used in the book is trying to punch a piece of paper with 200 N of force. When you apply force to the paper it will accelerate out of the way, thus you cannot apply a large action force.

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Thanks to our friends at NASA, we were able to get a picture of Newton's Third Law. As you can see with the Exhaust pushing backwards and towards the ground the Engine is trusted forward.



when the small child is pulling against the beastly man the force is equal to 500 N, and when he his rope is connected to the wall doing no pulling what so ever it equals 500 N. This shows how the forces always equal each other.