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B Confusion in Newton's 3rd law of motion

  1. Jul 15, 2016 #1
    I'm having a lot of confusions in the 3rd law of motion.It says action and reaction forces do not create equilibrium as the forces act upon two different bodies.Okay,I understand that if I want to make a body move I'll have to count the net force that is acting upon it not the force that is being exerted by it on another body.I can understand it when I see the example of the horse and cart problem or the boat and passenger problem that the passenger exerts a force on the boat and that's why the boat move though the boat exerts an equal force to the passenger that doesn't make any effect on the boat's movement. But, I get confused when I see the example of a book resting on a table.If the book exerting a force on the table then the table should break or move because the table is also exerting an equal force on the book but the book is a different object.How can it create an equilibrium then?I mean, I can't match the two of the examples and getting more and more confused.
    Please help me.
    With regards,
    Shafia.
     
  2. jcsd
  3. Jul 15, 2016 #2

    Doc Al

    User Avatar

    Staff: Mentor

    The book is in equilibrium because the net force on it is zero: The force of gravity (the earth) pulling down is canceled by the force of the table pushing up.

    The table is also in equilibrium: The force that the book exerts on the table plus the weight of the table is balanced by the upward force that the ground exerts on the table.

    It's true that the force that the book exerts on the table is equal and opposite to the force that the table exerts on the book. But so what?
     
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