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Quick Kinetic Energy question - only confirmation of answer needed.

  1. Oct 17, 2009 #1
    Hi guys,

    Calculate the change in kinetic energy of a car of mass 2000kg if it changes its velocity from 30km/h to 60km/h

    KE=1/2mv^2

    So, to find the change in KE, subtract its KE when it was going 30km/h from when it was going 60km/h.

    At 30km/h:
    KE=1/2mv^2
    KE=1/2*200*8.33^2
    KE=69389J

    At 60km/h:
    KE=1/2mv^2
    KE=1/2*2000*16.7^2
    KE=278890J

    So change in KE is 209501-69389
    = 209501J

    Is that correct, or am I doing it totally wrong?

    Also - "explain the source of the energy gain" - would that just be an increase in velocity?
     
  2. jcsd
  3. Oct 17, 2009 #2

    rock.freak667

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    Yes that is correct. The source would be what is producing motion in the car in the first place. So this would be the?
     
  4. Oct 17, 2009 #3
    The driving force/friction between the tires and the road?
     
  5. Oct 17, 2009 #4

    rock.freak667

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    Well I'd just say it is the engine.
     
  6. Oct 17, 2009 #5
    Alright great, thanks for your help! :)
     
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