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Specific Heat & Velocity relationship??

  1. Apr 19, 2016 #1
    [Mentor's note: this was originally posted in a non-homework forum and therefore does not use the homework template.]

    Hi everyone,
    I'm a bit stuck on this question and hoping someone could give me the solution.

    "A lump of lead, moving with a velocity of 22.0 m/s, is brought to rest. If 55.0% of the work done in stopping the lead is converted into heat, what will be the temperature rise of the lead? Take the specific heat of lead to be 1.30 x 10^2."

    In the answers, they just give the answer of 1.02 degrees Celsius. I can't figure out how they got there. Any help would be appreciated.

    Thanks
     
    Last edited by a moderator: Apr 19, 2016
  2. jcsd
  3. Apr 19, 2016 #2

    Nidum

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    What energy does the lump of lead have when it is moving ? What happens to that energy when the lump is brought to rest ?

    nb: Actual mass of the lump is not given in question so do all calculations for a mass M .
     
    Last edited: Apr 19, 2016
  4. Apr 19, 2016 #3
    The mass was not given in the question, which confused me.
     
  5. Apr 19, 2016 #4
    Go ahead and leave mass as a variable and see if the mass cancels out in the end.
     
  6. Apr 19, 2016 #5
    The question was asking to find out the unknown variable of the temperature change. If mass cancels out how would it be possible to determine the amount of energy?

    Is it possible to solve the question with the information provided?

    This is the first time I've ever taken physics as a subject so I'm a complete beginner.

    This was my first post and I realised I posted in the wrong section. (sorry!)
     
  7. Apr 20, 2016 #6

    Nidum

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    The lump of lead initially has Kinetic energy .

    KE = 0.5 * M * v^2 where M is the mass and v the velocity . Units N-m or Joule .

    On impact with whatever is bringing the lump to rest this energy is converted into heat and we are told that 55% of this heat goes into the lump .

    Now read about Specific Heat and see if you can complete the question .
     
    Last edited: Apr 20, 2016
  8. Apr 20, 2016 #7
    Thank you so much for your help!
    I got the right answer and you guys to thank.

    Have a nice day
     
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