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Homework Help: Its been a year now i'm back . help ? =D

  1. Nov 13, 2005 #1
    its been a year now i'm back . help plz ? =D

    hey guys it's been a while i haven't been on in a long time since last year when i last had physics 10 the introductory course and now i'm back just looking for guidance how to do this question ( helping friend :!!) anyways
    here it is:

    A racing car has a mass of 1500kg, is accelerating at 5.0m/s^2, is experiencing a lift force of 600 N up (due to its streamlined shape) and ground effects of 1000 N down (due to air dams and spoilers). Find the driving force needed to keep the car going given that uk = 1.0 for the car

    since it's been so long since i've last done physics the only equation that comes to mind is Fnet = ma but i'm sure that's wrong lol sooo can someone help me out? thanks !
  2. jcsd
  3. Nov 13, 2005 #2
    Welcome back.

    The equations you have written holds true for any situation. But in this case you may forget that whatever resultant force downward the car provides, will be provided equally in the opposite direction by the ground. So we know there will be NO net force UP or DOWN.

    Can you work out the FORCE that is needed to accelerate the car by this much (neglecting friction)?

    Now we have to consider friction. There will be a force of friction opposing this force you have worked out now. So we need to increase the force, by adding the magnitude of friction to the previous answer.

    Friction = Normal Force x Coefficient of kinetic friction

    What is the normal force? (Hint: don't forget about the objects WEIGHT).

    Hope this helps,
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