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laughs

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Newton's third law of motion

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Newton's third law of motion states

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for every action there is an equal and

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opposite reaction

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this third law always comes in pairs

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and is related to the force

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or push and pull upon an object

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if you have two objects one is doing the

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pushing

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and one is doing the pulling

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no matter how little the objects are

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moving

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and sometimes you can really see an

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action and a reaction

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in Florida at the Kennedy Space Center

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scientists use Rockets to launch space

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shuttles into orbit

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when the Rockets fire the exhaust from

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the rocket moves downward while the

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rocket moves upward

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without this law of motion the space

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shuttle would never have lifted off the

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ground and we would never have landed on

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the moon

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the force of action and reaction working

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together caused the shuttle to Launch

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you can't have one without the other

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want to see another example of Newton's

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third law

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what do you notice

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this time let's slow things down and see

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if we can identify the action and

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reaction force did you notice that the

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cannon moved backward when the

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Cannonball shot forward

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that backward movement is the Canon's

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reaction

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to the action of shooting The Cannonball

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just like with the space shuttle

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Newton also noticed that the amount of

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force on the first object always equaled

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the amount of force on the second object

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in other words the forces of action and

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reaction are always equal

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that means if a boxer punches a punching

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bag with 50 pounds of force

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that punching bag will also hit the

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boxer's fist with 50 pounds of force

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ouch

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if the boxer only gives 10 pounds of

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force with his fist

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his fist gets 10 pounds of force in

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return

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and if he gives five pounds of force

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he'll get five pounds of force back so

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if the forces of action and reaction are

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always equal

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how do you think this is going to end

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oh maybe don't try that one at home

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now that you know about actions and

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reactions think about the many reactions

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we cause every day

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let's talk about one last thing have you

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ever tried to move a heavy piece of

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furniture like a couch and did you

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wonder why it takes a minute for the

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couch to start moving this is because of

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something called static friction when

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you apply horizontal force from your

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body the floor is actually applying

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frictional force to the same object

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this continues until the object starts

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to move and then sliding friction

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happens

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sliding friction is the same Sensation

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that you get when you rub your hands

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together really fast and generate heat

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you don't have to push something as hard

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to keep it moving when you reduce the

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friction the less friction you have the

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less energy you use

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so the next time you're jumping on a

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trampoline or even sitting in a chair

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think about Newton's third law turns out

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there are actions and reactions

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happening everywhere you look

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hope you had fun learning with us

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