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Multi-concepts problem

  1. Mar 15, 2013 #1
    The picture below shows a block of mass 5.22kg held against a spring of spring constant compressed by a distance d = 28.3cm on a frictionless ramp of length . The ramp has an angle of 20°. A distance x = 1.16m separates the ramp from a landing area that is at the same height as the top of the ramp.

    http://session.masteringphysics.com/problemAsset/1000182266/40/114-24-1.png

    1.If the mass leaves the end of the spring at a speed of 4.43 , what is the spring constant of the spring?
    2.If the mass reaches the top of the ramp moving at speed 2.81 , what is the length of the ramp?
    Measure the length of the ramp from the starting point (compressed spring) as shown in the picture.
    3. Does the mass successfully jump the gap and land on the other side?



    I thought I could use W(work) = PEg+KE
    but that is as far as I got if someone could walk me through this I would greatly appreciate it I have a final next week on this and I want to make sure I'm doing it right.
     
    Last edited by a moderator: Mar 15, 2013
  2. jcsd
  3. Mar 15, 2013 #2

    haruspex

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    What changes in energy (kinetic, potential) occur as the spring goes from compressed to uncompressed? btw, I don't see a value for L. I assume all speeds are in m/s.
     
  4. Mar 15, 2013 #3
    L is the frictionless ramp of length and yes the speeds will be in m/s.

    the energy in this are well Spring, Kinetic and work. Could Gravitational Energy take place as the box goes up from the spring?
     
  5. Mar 15, 2013 #4

    haruspex

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    Yes, you have to take into account the gain in potential energy. Can you quantify the above changes and thus find the velocity at end of ramp?
     
  6. Mar 15, 2013 #5
    to find the velocity could I set up an equation like:

    W+PEs=KE

    I'm calculating now...hopefully it works
     
  7. Mar 15, 2013 #6

    haruspex

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    That doesn't look quite right, but maybe it's not what you meant. The sum of the energies is constant. You start with PE in the spring and finish with gravitational PE and KE at top of ramp.
     
  8. Mar 15, 2013 #7
    Since there's no Work involved because it is on a frictionless I will use PEs=KE+PEg
     
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