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applesjgtl

  • 3 years ago

A car weighing 1400kg accelerates from 90 km/hr to 110 km/hr in 6.0s. a) assuming no friction, what was the power output of the car? b) If a frictional force of 700 N acted on the car over a distance of 400 m during the same 6.0-second acceleration, what would be the power output of the car if the same speed increase was observed?

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  1. wio
    • 3 years ago
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    Figure out it's change in kinetic energy.

  2. wio
    • 3 years ago
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    You have the mass and two velocities. So calculate the kinetic energy before and after acceleration.

  3. wio
    • 3 years ago
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    Power is just going to be energy / time

  4. wio
    • 3 years ago
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    kinetic energy is 1/2 mass * velocity^2

  5. wio
    • 3 years ago
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    You probably want to convert units to m/s

  6. applesjgtl
    • 3 years ago
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    Multiply by 1000 and divide by 3600?

  7. wio
    • 3 years ago
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    Yes

  8. wio
    • 3 years ago
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    For b) " 700 N acted on the car over a distance of 400 m" Just remember that work = force * distance that will tell you how much energy was taken away

  9. wio
    • 3 years ago
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    so subtract that out and calculate the power again.

  10. wio
    • 3 years ago
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    @applesjgtl got it?

  11. applesjgtl
    • 3 years ago
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    For part a, what value do I use for energy? Is it KE2-KE1?

  12. applesjgtl
    • 3 years ago
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    @wio, still there?

  13. wio
    • 3 years ago
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    For part a) use energy

  14. wio
    • 3 years ago
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    then divide the change in energy by time to get power output.

  15. applesjgtl
    • 3 years ago
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    Here's what I have

  16. applesjgtl
    • 3 years ago
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    Oh, I get it. Thanks for your help!

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