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Kinetic energy to thermal energy

  1. May 15, 2015 #1
    1. The problem statement, all variables and given/known data
    upload_2015-5-14_23-5-6.png

    2. Relevant equations

    Q = c m ΔT
    3. The attempt at a solution
    so converting 55 mph to meters per sec gives me a velocity of 24.58 m/s

    kinetic energy of car is 1/2 m v2

    i set 1/2 m v2 = c m ΔT



    plugging in v and c and masses of both

    ΔT = 134.56

    is that correct?
     
  2. jcsd
  3. May 15, 2015 #2

    Orodruin

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    There is a central piece of information missing here: How many brakes does the car have? That is, how many of the car's wheels have brakes.
     
  4. May 15, 2015 #3
    so there is no way i can answer this question? or do i just assume its 4? 1 for each wheel
     
  5. May 15, 2015 #4

    Orodruin

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    Unless you are a mind reader, no. I am not very familiar with cars, but I would assume that either all wheels or one pair of wheels would have brakes.
     
  6. May 15, 2015 #5
    So if we choose 4 wheels as it is most common, then has moment of inertia a role here?
     
  7. May 15, 2015 #6

    haruspex

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    In principle, yes, but we have no information on the moments of inertia of the wheels or their radius. Besides, it would be small compared with the linear KE of the vehicle.
     
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