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Homework Help: Two cars travel at the same speed of 105 km/h

  1. Jan 13, 2010 #1
    Two cars travel at the same speed of 105 km/h. One of the cars, a sleek sports car, has a motor that delivers only 35 kW of power at this speed. The other car's motor needs to produce 65 kW to move the car at this speed. Forces exerted from air resistance cause the difference.

    A) For each car, list the external horizontal forces exerted on it, and give the cause of each force. Compare their magnitudes.
    B) According to Newton's third law of motion, each car exerts forces. What are the directions of these forces?
    C) Calculate the magnitude of the forward force exerted by each car on the air.
    D) The car engines did work. Where did the energy they transferred come from?

    I really have no clue where to begin when solving this problem, and I'd love some help if anyone knows how to do this! Thank you sooo much!
  2. jcsd
  3. Jan 13, 2010 #2
    Hi there,

    Probably the best tip one can give you is to make a drawing of the situation. It does not have to be pretty (we are not artist, but doing physics), just explaning the situation. Once you have you two cars drawn, then imagine what are the forces acting upon them. The rest should come easily.

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