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Homework Help: What fraction of the kinetic energy is converted to other forms in collision?

  1. Jul 31, 2012 #1
    1. The problem statement, all variables and given/known data
    there are 2 blocks along a frictionless track. block 1 has a mass of m1 and block 2 has a mass of m2. Block 1 is initially moving at a speed of v0. it collides and sticks to the initial stationary block 2. (m2=9m1) what fraction of the inital kinetic energ of the system is converted to other forms (heat, sound...) as a result of the collision?

    1)1%
    2)10%
    3)50%
    4)90%
    5)95%


    2. Relevant equations
    I sort of think this as more of a general knowledge question... this is the 2nd part. the first part ask you to calculate the velocity after collision


    3. The attempt at a solution
     
  2. jcsd
  3. Jul 31, 2012 #2
    The figure out part 2, you need to solve part 1.
     
  4. Jul 31, 2012 #3
    the answer to part 1 is 1/10v0, if I'm not wrong. Used momentum formula.
     
  5. Jul 31, 2012 #4
    Correct. Now you just need to compute the total kinetic energies before and after the collision, and compare them.
     
  6. Jul 31, 2012 #5
    yay yay thank you!

    initial:final=1 x v^2 : 10 x (0.1v)^2=1:0.1
    so 90% of KE was converted to other forms! Thank you once again:D
     
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