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Homework Help: Porsche's max speed

  1. Mar 24, 2009 #1
    A Porsche 944 Turbo has a rated engine power of 217 hp. 30% of the power is lost in the drive train, and 70% reaches the wheels. The total mass of the car and driver is 1530 kg, and two-thirds of the weight is over the drive wheels.

    okay... sooo....

    I know that P = F(car)*velocity = m*g*v+1/4*A*v^3
    where A is the cross-section area.
    But this problem doesn't have a cross-section area given.

    Since the maximum power output is 217 hp and 70% of the power reaches the drive wheels.
    P= (217hp)(0.70) = 151.9 hp

    151.9hp * 746W/hp = 113317.4 W
    and i don't know where to go with this.
  2. jcsd
  3. Mar 24, 2009 #2
    113317.4 W reaches the wheels.The total weight of the wheels = 2/3 * 1530 * 9.8
    I reckon that should help you find the velocity.
  4. Mar 24, 2009 #3
    okay uh... the thing is...

    I know P=F*v right?
    so, if P= 113317.4
    and F= 9996

    i get v= 11.336 m/s...
    and that is not nearly enough for a porsche to reach it's max speed.... it's like the min speed if anything.
  5. Mar 24, 2009 #4
    nvm i got it! hahaha ;) thanks!
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