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Physics 11 help please ?

  1. Dec 15, 2008 #1
    1. The problem statement, all variables and given/known data

    A 55 kg student wearing skates stands at rest on a frictionless horizontal ice surface. She throws a 10 kg backpack horizontally with a speed8.3 m/s .
    What is the velocity of the student after she throws the backpack?

    2. Relevant equations

    F[tex]\Delta[/tex]t = m[tex]\Delta[/tex]v

    3. The attempt at a solution
    so the answer should be 1.5 m/s [N] and i got this by dividing 10 kg (backpack) by 55 kg (student) and then multiplying that answer by 8.3 m/s . is this the right way or is there a proper formula i should follow?
    thanks !
     
  2. jcsd
  3. Dec 15, 2008 #2

    Doc Al

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    Staff: Mentor

    That's correct. The impulse given to the backpack will be exactly equal and opposite to the impulse given to the student. Thus:
    mstudent*vstudent = mbackpack*vbackpack

    Just solve for vstudent.
     
  4. Dec 15, 2008 #3
    great, thanks ! :smile:
     
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