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B Newton's Laws of Motion

  1. Jan 16, 2017 #1
    When a keep two blocks one over another...And apply a foce on the block which is below...Why does the upper block falls down..Why dosent it move with A? assumin there's no friction between A and B?
     
  2. jcsd
  3. Jan 16, 2017 #2

    phinds

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    Why do you think? Which of Newton's Laws might apply to this situation?
     
  4. Jan 16, 2017 #3
    No idea
     
  5. Jan 16, 2017 #4

    phinds

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    Well, look at it this way. You are surprised that the upper block falls down when the lower block moves out from under it. Ask yourself why SHOULD the upper block move with the lower block?
     
  6. Jan 16, 2017 #5

    ZapperZ

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    Aren't you being a bit lazy here?

    Try this. How about you write down, in this thread, all 3 of Newton's Laws? You may copy that from your text, but better yet, state them in your own words to see if you actually not just read them, but comprehend what they say. Then we can jump off from there.

    Zz.
     
  7. Jan 17, 2017 #6
    First Law states that A body continues to be in motion or at rest until an unbalanced force is acted on it
    Second law-sEOCND LAW - f=MA
    Third Law: Every action has an equal and opposite reaction
     
  8. Jan 17, 2017 #7

    ZapperZ

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    Now, look at your question, and then look at the First Law. In particular, if there's no friction between A and B, how would the First Law be relevant here?

    Zz.
     
  9. Jan 17, 2017 #8
    The Normal and Mg cancel out,no friction means no other force acting on B,right?
     
  10. Jan 17, 2017 #9
     
  11. Jan 17, 2017 #10

    phinds

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    RIght. And what happens to a body with no force acting on it?
     
  12. Jan 17, 2017 #11
    It remains unaccelerated, So when we apply force on the lower bloack,the upper block will stay where it is and the lower block will mover forward, am i right?
     
  13. Jan 17, 2017 #12

    phinds

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    yes, that's where I was leading you in post #4
     
  14. Jan 17, 2017 #13
    Thank you :)
     
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