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Homework Help: Need some HW help please

  1. Oct 17, 2004 #1
    Hey if anyone could please tell me how to do this it would be a great help.

    ok the question asks about an accelerating car. The mass of the car is 1200kg. When the engine is floored it creates a constant forward force of 9600N. The drag created by the car is equal to this equation: D=160v. Determine the velocity of the car after it has been floored for 8 seconds.
     
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  3. Oct 17, 2004 #2

    Tide

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    You just need to solve the equation of motion:

    [tex]m\frac {dv}{dt} = 9600 - 160 v[/tex]

    Just remember to keep your units consistent!
     
  4. Oct 17, 2004 #3
    actually i am not familiar with that equation. and my calculus is poor. So if anyone could explain this further, thanks!
     
  5. Oct 18, 2004 #4

    HallsofIvy

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    [tex]1200\frac {dv}{dt} = 9600 - 160 v= 160(60- v)[/tex]
    is the same as
    [tex]\frac{dv}{60-v}= \frac{160}{1200}dt= \frac{1}{20}dt[/tex]

    To integrate the left side, let u= 60- v so that du= -dv and the equation becomes
    [tex]-\frac{du}{u}= \frac{1}{20}dt[/tex]

    You ought to be able to integrate that.
     
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