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
#4
emailanmol
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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.