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Lost Postential Energy

  1. Feb 23, 2009 #1
    1. The problem statement, all variables and given/known data

    A mass 0.40 kg is released and slides down the incline. The maximum velocity ( taken the instant before the mass reaches the bottom of the incline ) is 1.00 m/s. What is the kinetic energy at that time? What percentage of the potential energy of the system is not converted into kinetic energy due to friction? (converted into heat instead)

    I dont quite understand how to find out the percent of potential energy lost..thanks for any help!

    2. Relevant equations

    I solved for the kinetic energy correctly by using

    W=KE=1/2mv^2


    3. The attempt at a solution

    =1/2(.4)(1)^2
    =.2 Joules

    i'm not sure about how to solve for the percent of potential energy lost..thanks
     
  2. jcsd
  3. Feb 23, 2009 #2

    LowlyPion

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    You're going to need to know the height to figure the PE.
     
  4. Feb 23, 2009 #3
    The height is 7 cm (.007 m)
     
  5. Feb 23, 2009 #4
    Potential Energy!

    1. The problem statement, all variables and given/known data

    A mass 0.40 kg is released and slides down the incline. The maximum velocity ( taken the instant before the mass reaches the bottom of the incline ) is 1.00 m/s. What is the kinetic energy at that time? What percentage of the potential energy of the system is not converted into kinetic energy due to friction? (converted into heat instead)

    The height of the incline is 7 cm..and the hypotenuse is 40 cm

    I dont quite understand how to find out the percent of potential energy lost..thanks for any help!

    2. Relevant equations

    I solved for the kinetic energy correctly by using

    W=KE=1/2mv^2


    3. The attempt at a solution

    =1/2(.4)(1)^2
    =.2 Joules

    i'm not sure about how to solve for the percent of potential energy lost..thanks!
     
  6. Feb 23, 2009 #5

    LowlyPion

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    OK. So what is the potential energy available to go to kinetic?

    How much does it need to go 1 m/s? Well you found that.

    So how much potential isn't accounted for in going to kinetic?
     
  7. Feb 23, 2009 #6

    rl.bhat

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    Re: Potential Energy!

    What is the potential energy at the top of the inclined plane?
     
  8. Feb 23, 2009 #7
    Re: Potential Energy!

    Is it .2744 Joules?
     
  9. Feb 23, 2009 #8

    LowlyPion

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