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# What is the 3rd of Newton's laws?

2 years ago

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114 Replies

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Reginald Wisoky

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When two objects interact, the forces they exert on each other are equal and opposite.

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Teo Cristobal

for every action there is an equal and opposite reaction

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The third of Newton's law states that action and reaction are equal but opposite

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Latoya

Newton's 3rd law is as follows: All forces come in pairs. These forces are:

1. the same type of force (e.g. both are gravitational)
2. have the same size (magnitude)
3. act in opposite directions to one another
4. act at the same time,
5. act on different objects

The 'action = reaction' referred to is this pair of forces that must fit all of these 5 points to be considered an action-reaction pair.

A common mistake is thinking that a book lying on a table has weight and normal reaction as its action-reaction pairs. This is incorrect because a) both forces act on the same object (the book) and b) these are not the same type of force - normal reaction is electromagnetic whereas the weight of the book is gravitational. The fact that both of these forces have the same magnitude and act in opposite directions is an example of equilibrium instead.

But all forces come in pairs so what are the other 2 forces that do make up the action-reaction pairs? Well the first is the gravitational pull from the Earth, this forms the action-reaction pair with the weight of the book. Secondly, the normal reaction of the book onto the table with the normal reaction of the table onto the book forms the other action-reaction pair.

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Akanksha Saroch

For every action there is equal and opposite reaction

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The 3rd law of Newton states that when two bodies interact, they apply forces to one another that are equal in magnitude and opposite in direction. The third law is also known as the law of action and reaction.

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Gurjivan Singh Nahal

When two objects interact, they exert forces on each other which are equal in magnitude and opposite in direction

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For every force in nature there is an equal and opposite reaction

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For every action, there is an equal and opposite reaction.

Some people get this confused, these two forces are not both acting on the same object, your weight force and the reaction force from the ground do not count as an equal and opposite pair.

Sometimes the reaction force from the ground might be smaller or greater than your weight force, for example when you are in a lift.

An example of an equal and opposite pair is the reaction force the ground exerts on you, and the force you exert on the ground.

Newton's third law refers to the forces two different objects exert on each other.

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Anam Asif

For every action, there is an equal and opposite reaction

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Yi Kiu Tong

The third law is known as the law of action and reaction. It states that when two bodies interact, they apply forces to one another that are equal in magnitude and opposite in direction.

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Liza Khan

Every action has an equal and opposite reaction.

i.e if object A exerts a force on object B, then object B must exert a force of equal magnitude and in the opposite direction to object A.

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Hi Reginald,

Newton's 3rd Law of Motion states that for every force there is an equal and opposite and force in nature.

This means that if there are to objects, object A and object B, and object A exerts a force of 60N on the right onto object B, then object B must exert an equal force of 60N in the opposite direction.

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Shubhdeep Sethi

Every force has an equal and opposite reaction. (Easier way might be to think momentum is always conserved)

H
Hamdaan Sheikh

Formally known as; When Body A exerts a force upon Body B, Body B will exert an equal and opposite force upon Body A

A more commonly known phrase is; "every action has an equal and opposite reaction"

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