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Elastic potential energy

  1. Nov 10, 2011 #1
    1. The problem statement, all variables and given/known data
    A horizontal spring, of force constant 12N/m, is mounted at the edge of a lab bench to shoot marbles at targets on the floor 93.0 cm below. A marble of mass 8.3 x 10^-3kg is shot from the spring, which is initially compressed a distance of 4.0 cm. how far does the marble travel horizontally before hitting the floor?


    2. Relevant equations
    Ee= 1/2kx^2
    Ep=mgh
    Ek=1/2mv^2 ?
    W= Fd?
    3. The attempt at a solution

    not sure how to start it off
     
  2. jcsd
  3. Nov 10, 2011 #2
    First let us find the initial velocity with which the marble is projected.

    What principle do you think we will use?
     
  4. Nov 10, 2011 #3

    Doc Al

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    Staff: Mentor

    Start by figuring how fast the marble is moving when it leaves the spring.
     
  5. Nov 10, 2011 #4
    ok i did that and i got 1.52m/s by using the law of conservation energy "Ee=Ek"
     
  6. Nov 10, 2011 #5
    correct
     
  7. Nov 10, 2011 #6

    Doc Al

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    Staff: Mentor

    Good.

    Now you can treat the rest as a projectile motion problem. How long does it take for the marble to hit the floor?
     
  8. Nov 10, 2011 #7
    Now this is the speed with which the marble is projected horizontally onto the floor below.
     
  9. Nov 10, 2011 #8
    we never have touch upon projectile motion in class. is there some other method?
     
  10. Nov 10, 2011 #9
    in projectile motion the vertical motion is independent of the horizontal motion.

    Hence one can treat projectile motion as the resultant of two linear motions. So just work in linear motion. But be careful whether you are working in the vertical or in the horizontal.
     
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