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Forces misconception hammer and nail

  1. Nov 3, 2011 #1
    Can someone please explain how a hammer can drive a nail. A person swings a hammer in the air and exerts a force on a nail but newton's third says the nail exerts the same force back on the hammer. So if newton is right then how does the nail accelerate.

    I just don't get it.
     
  2. jcsd
  3. Nov 3, 2011 #2

    A.T.

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    What exactly don't you get about it?
     
    Last edited by a moderator: Jun 5, 2015
  4. Nov 3, 2011 #3

    Pengwuino

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    The hammer does get accelerated backwards (as in up). What do you think stops the motion of the hammer as you slam down on the nail?
     
    Last edited by a moderator: Jun 5, 2015
  5. Nov 3, 2011 #4
    I guess my question might be is the hammer able to exert a force on the nail because it has mass and acceleration?
    Also if the nail exerts the same force back then how does the nail accelerate
     
  6. Nov 3, 2011 #5
    If i have a coffee mug on a table why am i able to push it with my hand if whenever i push it the coffee mug pushes back.
     
  7. Nov 3, 2011 #6
    Thats what im trying to get at and i feel extremely stupid right now but im just not getting it
     
  8. Nov 3, 2011 #7

    A.T.

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    Why should the force on the hammer prevent the nail from accelerating?
     
    Last edited by a moderator: Jun 5, 2015
  9. Nov 3, 2011 #8
    because the force on the hammer is equal to the force on the nail
     
  10. Nov 3, 2011 #9
    so shouldnt the forces on the nail and hammer just go away if newtons law is true
     
  11. Nov 3, 2011 #10

    Pengwuino

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    You exert the same force that the coffee mug exerts on you. However, since you have a far far greater mass, by F = ma, the coffee mug will provide a very small (and to you, unnoticeable) acceleration back on you compared to the acceleration you provide to the mug.
     
    Last edited by a moderator: Jun 5, 2015
  12. Nov 3, 2011 #11
    oooooo
     
  13. Nov 3, 2011 #12

    A.T.

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    But it is acting on the hammer. Why should it affect the nail?
     
    Last edited by a moderator: Jun 5, 2015
  14. Nov 3, 2011 #13

    A.T.

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    Why? They act on two different objects.
     
    Last edited by a moderator: Jun 5, 2015
  15. Nov 3, 2011 #14
    well im thinking that theres a force acting on the hammer just as theres a force acting on the nail
     
  16. Nov 3, 2011 #15

    A.T.

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    Yes, and therefore they both are accelerated in opposite directions.
     
    Last edited by a moderator: Jun 5, 2015
  17. Nov 3, 2011 #16
    i just dont get why theres acceleration if the force of the hammer is the same and opposite the force on the nail. To me it seems like the force should just go away if thats the case
     
  18. Nov 3, 2011 #17
    says to self: "why is this so hard for me to understand"
     
  19. Nov 3, 2011 #18
    but why should i be providing acceleration if the force is canceled. Doesn't there have to be some outside force. When i push on a car the car pushes on me. The only way for me to move the car / accelerate it is if i push on the ground really hard.
     
  20. Nov 3, 2011 #19

    A.T.

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    They don't cancel, because they act on different objects.
     
    Last edited by a moderator: Jun 5, 2015
  21. Nov 3, 2011 #20

    Dale

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    This is not correct. If the ground were frictionless so that neither you nor the car could push on the ground then when you push on the car you would accelerate in one direction and the car would accelerate in the opposite direction.
     
    Last edited by a moderator: Jun 5, 2015
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