applesjgtl
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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wio
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Figure out it's change in kinetic energy.
wio
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You have the mass and two velocities. So calculate the kinetic energy before and after acceleration.
wio
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Power is just going to be energy / time
wio
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kinetic energy is 1/2 mass * velocity^2
wio
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You probably want to convert units to m/s
applesjgtl
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Multiply by 1000 and divide by 3600?
wio
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Yes
wio
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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
wio
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so subtract that out and calculate the power again.
wio
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@applesjgtl got it?
applesjgtl
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For part a, what value do I use for energy? Is it KE2-KE1?
applesjgtl
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@wio, still there?
wio
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For part a) use energy
wio
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then divide the change in energy by time to get power output.
applesjgtl
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Here's what I have
applesjgtl
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Oh, I get it. Thanks for your help!