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Car Brakes and Thermal Energy

  1. Feb 12, 2009 #1
    1. The problem statement, all variables and given/known data
    Proper design of automobile braking systems must account for heat buildup under heaving braking. Calculate the thermal energy dissipated from brakes in a 1260-kg car that descends a 18.5° hill. The car begins braking when its speed is 102 km/h and slows down to a speed of 34 km/h in a distance of 0.51 km measured along the road.

    I honestly have no idea how to do this.
  2. jcsd
  3. Feb 12, 2009 #2


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    Think about how much potential energy as well as kinetic energy must be accounted for by the work of breaking over that distance.
  4. Feb 12, 2009 #3


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    Hi Stryder_SW! :smile:

    Virtually all the mechanical energy lost goes into heat (thermal energy), so …

    Hint: use the work-energy theorem … work done by the brakes = mechanical energy lost. :wink:
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