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+K Physics/electicity help

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Waldo-
Posts: 1026 - Karma: 184

+K for a right answer

An electric car is designed to run off a bank of 12.0 V batteries with a total energy storage of 2.00*107 J.    Motor draws 5Kw with current of 416.7 Amps

If the electric motor draws 5.00 kW as the car moves at a steady speed of 20.0 m/s, how far can the car travel before it is "out of juice"?

Jan 19 2010 6:50PM
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Arabian.
Posts: 9632 - Karma: 55
Any weather conditions?
Jan 19 2010 6:52PM
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Palardy
Posts: 176 - Karma: 11
Well

This is all in ideal conditions, which is never true but

1) Find the time that the motor can run for, 2*10^7 J / 5.00kW (or 5000 J/s)
This will give you the number of seconds the car will be able to run for.

2) Multiply the speed 20m/s by the time in seconds to see how many meters it will go.

The voltage and Amps tell you nothing unless you are worrying about the internal resistance, max discharge rate, resistance of wires, ect, ect and all the other imperfections in the system. But I'm assuming you are meant to treat this battery as an ideal voltage source.

Good luck
Jan 19 2010 8:29PM
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notomatoplz
Posts: 1377 - Karma: 29
+K for reminding me to study for my physics final:(
Jan 19 2010 8:38PM
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anxju
Posts: 9371 - Karma: 61
its a trick question, i snuck a Hi-C in a secret compartment where no one will find it. your car will never run out of juice
Jan 19 2010 8:40PM
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TheButterHashira
Posts: 9691 - Karma: 1,702
Well if you are worried about resistance it should be the voltage over the current. But it seems like it might just be extra information you don't need. Go with the guy above.
Jan 19 2010 8:42PM
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ir1sh
Posts: 61 - Karma: 28
ahahahahaha +k to you sir
Jan 19 2010 10:56PM
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Waldo-
Posts: 1026 - Karma: 184
got it. its 80.  and i found the Hi C. thats stuff is gooood
Jan 20 2010 8:28AM
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anxju
Posts: 9371 - Karma: 61
nah dude, that one was just a decoy. the real one is inside the stuffing of the passenger's seat. if you really want it, be my guest
Jan 22 2010 5:58PM
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flexpattern
Posts: 1090 - Karma: 45
oh i just worked it out without reading the rest of the thread what a noob....

but i felt my tribulations shouldn't go to waste so just to let you know that i also got 8000m which is 80km... i think that sounds a reasonable range for an electric car so i think thats probably the answer!

you didn't have to worry about the amp/ volts part, that was just to confuse you!
Jan 22 2010 6:17PM
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feihlination
Posts: 8356 - Karma: 1,084
last time i checked, 8000m wasnt 80 km

Jan 22 2010 7:13PM
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flexpattern
Posts: 1090 - Karma: 45
pwned. The source you must have checked was indeed correct !

typo my friend - my finger on the 0 was too lazy to push that final 0 to take it to 80000m ..... which would have been 80km...
Jan 22 2010 7:22PM
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