Kinetic Energy problem i think

  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. LowlyPion

    LowlyPion 5,324
    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. then change in kinetic energy equals the work done, which one requires more work?
  5. 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. LowlyPion

    LowlyPion 5,324
    Homework Helper

    That should do it.
  7. Thank you very much!!! :!!)
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