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Homework Help: Car accelerating on ramp - power of engine

  1. Nov 12, 2007 #1
    1. The problem statement, all variables and given/known data

    A car accelerates at 1 m/s^2 up a ramp which makes an angle of 5 degrees with the horizontal. Ignoring friction and air resistance what fraction of the power the engine puts into the car's motion goes into the car's kinetic energy?

    2. Relevant equations

    3. The attempt at a solution

    I don't know how to attempt this problem I know the answer is 54% because this is a review problem for my test which is coming up, but how is power related to kinetic energy?
  2. jcsd
  3. Nov 12, 2007 #2
    Power is energy (or work) per second.

    Where is the energy from the engine going apart from into kinetic energy, KE?
  4. Nov 12, 2007 #3
    some would have to be going into potential energy right? theres no friction or air resistance so nothing else could be taking energy
  5. Nov 12, 2007 #4
    well I got to the correct answer I decided to measure the problem after the car had traveled 1 meter, used kinematics to find the final speed then put

    KE/(KE+PE) and it worked out because the masses canceled out and i got .538 which is correct will the method always work out if there is no friction or any other forces to worry about. It seems like this isn't the correct way to do it.
  6. Nov 12, 2007 #5


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    Science Advisor
    Homework Helper

    That's correct, if you ignore friction conservation of energy is always correct - and is often the simplest way to do it.
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