# What are some examples of Newton's third (3rd) law?

accelerate23
If you want, could you give me at least 5 so that I can fully understand.

azizlwl
http://en.wikipedia.org/wiki/Newton_third_law

A ball hang by a string which attached to a ceiling.
The ball pull the string down, the string pull the ball up.
The string pull the ceiling down, the ceiling pull the string up

emailanmol
Newtons third law states that if an object A applies a force on object B (called action)

Object B applies an equal and oppsite force on object A (called reaction).

REMEMBER: Action and Reaction forces always act on different object.

IF ACTION ACTS ON B , then REACTION ACTS ON A.

Eg 1

The Earth pulls you by force mg towards it, you pull the Earth towards yourself with reaction force whose value is also mg.

Eg 2:
Cristiano Ronaldo applies a force on ball to kick it, the ball applies the same force on Ronaldo which is the reaction.

Eg 3:

When i pressed the key 3 on my keyboard with a force, the key pushed back on me with a reaction force.

Eg 4: this is an imp one.

a book rests on a table.
The Earth is pulling it down with force mg.
However, the table is applying an opposing force F which balances mg to keep the book at rest.

HOWEVER, THE FORCE F IS NOT THE REACTION FORCE TO mg.

remember, action and reaction always act on different objects.

Here both F and mg both act on A so they can't be action reaction pair.

In fact, The reaction force of mg on book by earth, is actually acting on earth.

The reaction of force F on book by table acts on table.

In this particular case F=mg which is why the book is at rest, but they are not action reaction forces.

Eg 5: Another imp one.

While walking we apply a force on Earth in backward direction with our feet.
Its reaction acts on us and pushes us forward making us walk.

Hope this helps.

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