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Block in a Curved Ball

  1. Oct 11, 2007 #1
    A 0.30-kg block slides along a small track with elevated ends and a flat central part. The flat part has a length L = 1.55 m. The curved portions of the track are frictionless, but for the flat part the coefficient of kinetic friction is 0.106. The block is released from rest from a height h = 82 cm on the left curved portion of the track. Calculate the maximum height reached by the block on the right curved portion of the track.

    img: http://i242.photobucket.com/albums/ff106/jtdla/prob09.gif

    The only thing I have figured out is the Potential Energy at the top, then the KE at the bottom.

    .3*9.8*.82=1/2*.3*x^2, that will yield a velocity. Outside of that, would I just treat the other part like a FBD
     
  2. jcsd
  3. Oct 11, 2007 #2

    learningphysics

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    Work done by friction = final energy - initial energy

    final energy = Work done by friction + initial energy
     
  4. Oct 11, 2007 #3
    Would I just calculate friction and then multiply it by the length of the bowl?

    N=mg
    muN=frictional force
    muN*length of bowl
     
  5. Oct 11, 2007 #4

    learningphysics

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    yes. remember that the frictional work is negative... so work by friction is -muN*length of bowl.
     
  6. Oct 11, 2007 #5
    by initial energy, do you mean potential energy
     
  7. Oct 11, 2007 #6

    learningphysics

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    yes. both initial and final energies are just potential energy...
     
  8. Oct 11, 2007 #7
    Won't this just calculate a velocity.

    I got 3.58 m/s

    1/2*.3*x^2=-.31164*1.5+.3*9.8*.82
     
    Last edited: Oct 11, 2007
  9. Oct 11, 2007 #8

    learningphysics

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    No. write out the equation.
     
  10. Oct 11, 2007 #9
    Oh!

    So would it be the potential energy of both sides of the bowl, except on one side i would have an unknown height

    mgh (left)-work of friction=mgh(right)
     
  11. Oct 11, 2007 #10

    learningphysics

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    yeah. what answer did you get?
     
  12. Oct 11, 2007 #11
  13. Oct 11, 2007 #12
    A skier (m=59.00 kg) starts sliding down from the top of a ski jump with negligible friction and takes off horizontally. If h = 7.70 m and D = 12.90 m, find H.

    Could I solve this problem in a similar manner?

    At the point where the skier is about to go off the ramp, is that both a PE and a KE.
     
  14. Oct 11, 2007 #13

    learningphysics

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    I don't understand the question... what are h, D and H? can you describe or post the picture?
     
  15. Oct 11, 2007 #14
  16. Oct 11, 2007 #15

    learningphysics

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    Use kinematics to get the velocity at h when it goes off the ramp... then use energy conservation to get the height H.
     
  17. Nov 27, 2011 #16
    My question is similar:

    A 0.40-kg block slides along a small track with elevated ends and a flat central part. The flat part has a length L = 1.41 m. The curved portions of the track are frictionless, but for the flat part the coefficient of kinetic friction is 0.145. The block is released from rest from a height h = 52 cm on the left curved portion of the track. Calculate the maximum height reached by the block on the right curved portion of the track.

    I did:
    Energy initial + work done by friction = Energy final
    mgh + F*x = mgh

    (mgh+F*x)
    ----------- = h
    (mg)

    [((0.4)(9.8)(0.52))+((0.145*-9.8)*(0.52))]
    ----------------------------------------- = h = 0.008875m
    ((0.4)(9.8))

    But the real answer is: 0.31555m
    Can anyone point out my mistake?
    Thank you for the assistance!
     
  18. Nov 27, 2011 #17
    I found my mistake... I used 9.8 as my force of friction. After 3 hours of doing this problems different ways... I finally found it! Thanks!
     
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