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Find momentum

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  1. Dec 17, 2014 #1
    (Mentor's Note: Thread moved from general physics after being replied to, hence the lack of a template)

    Find the momentum of a 50g bullet whose kinetic energy is 250J.
    I know the formula to find momentum is P= mv. Please give me hints
     
    Last edited by a moderator: Dec 17, 2014
  2. jcsd
  3. Dec 17, 2014 #2

    Bystander

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    Can you find "v" from what you've been given?
     
  4. Dec 17, 2014 #3
    No, the question only gave me 50 g bullet and 250J
     
  5. Dec 17, 2014 #4

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    You have been given a definition/formula for kinetic energy?
     
  6. Dec 17, 2014 #5
    Th
    The formula the teacher gave are p=mv and FT= delta P
     
  7. Dec 17, 2014 #6

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    This is the definition of momentum, and you've indicated you understand it.
    "Force x time (which is impulse) equals change in momentum." The bullet before it is fired has zero velocity and zero momentum. The change in momentum then is just "mv" from the first definition. So, all you need to find now is force and time.

    Are you absolutely certain you haven't been given any other definitions or formulas for kinetic energy, force, mass, work?
     
  8. Dec 18, 2014 #7
    No
     
  9. Dec 18, 2014 #8

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    Kinetic energy is defined as Ek = mv2/2 . I cannot believe that you haven't seen this in class or in the teaching materials or textbooks before being asked the original question.
     
  10. Dec 19, 2014 #9

    ehild

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    The problem gives mass and kinetic energy.

    You should know what kinetic energy is. Look after in your lecture notes. Or you can browse the Net. See, for example: http://www.physicsclassroom.com/class/energy/u5l1c.cfm
     
  11. Dec 21, 2014 #10
    (Attached image removed by moderator, provided the answer to the OPs homework question.)

    -----------------------

    Örsan Yüksek
     
  12. Dec 21, 2014 #11

    ehild

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    Correct!
     
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