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Homework Help: Kinetic Energy problem i think

  1. Mar 4, 2009 #1
    1. The problem statement, all variables and given/known data

    What takes more energy? Accelerating a car from 10-20m/s or from 20-30m/s? Why?

    2. Relevant equations

    3. The attempt at a solution

    Since KE = 1/2mv^2, I suppose the higher the velocity is the more kinetic energy the car will have, but I have no clue how to solve this problem.
  2. jcsd
  3. Mar 4, 2009 #2


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    Homework Helper

    Won't the bigger change in kinetic energy require the greater energy?
    You know that conservation of energy thing?

    Plug in the numbers.
  4. Mar 4, 2009 #3
    then change in kinetic energy equals the work done, which one requires more work?
  5. Mar 4, 2009 #4
    so is this right? since m is constant it is just 1kg

    1/2(1kg)(10m/s)2 = 50 joules
    1/2(1kg)(20m/s)2 = 200 joules
    1/2(1kg)(30m/s)2 = 450 joules

    KE for (10-20m/s) = 150 joules
    KE for (20-30m/s) = 250 joules

    So accelerating from 20-30m/s requires 100 more joules of energy?
    Last edited: Mar 4, 2009
  6. Mar 4, 2009 #5


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    That should do it.
  7. Mar 4, 2009 #6
    Thank you very much!!! :!!)
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