 ###### Matt Jones

M.Ed., George Washington University
Dept. chair at a high school

Matt is currently the department chair at a high school in San Francisco. In his spare time, Matt enjoys spending time outdoors with his wife and two kids.

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# Law of Action and Reaction - Newton's Third Law of Motion

Matt Jones ###### Matt Jones

M.Ed., George Washington University
Dept. chair at a high school

Matt is currently the department chair at a high school in San Francisco. In his spare time, Matt enjoys spending time outdoors with his wife and two kids.

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The Newton's Third Law of Motion states that for every action there is an equal and opposite reaction. Simply put, it means that every force can be undone. Mathematically, it means that for every vector there is another vector with opposite direction and equal magnitude.

Let's talk about the law of action and reaction, this is also known as Newton's third law and this simply states that for every action there's an equal and opposite reaction. So if I apply a force onto an object there's a reaction force that's applied back on the force that's been applied to it okay. And we can say that, the force is going to equal, I'm sorry we'll just say f1 is going to equal negative 2 so these forces apply in opposite directions and they cancel each other out. So you don't usually have to solve problems with this but you'll often times be asked in a question say for example if a big bat is hitting a ball at a thousand Newtons what is the force of the force of the ball on the bat? And you might be confused because the bat is big and the ball is small but remember for every action there's an equal and opposite reaction.

Which means simply that the ball is putting the same force of a thousand Newtons on the bat. So really regardless of size they're equal and opposite forces applied to each other. So that's a question you might see on a Physics problem and you can answer it again using Newton's third law of motion.