Posted by **HELP** on Sunday, September 18, 2011 at 2:37pm.

A 280 electric motor is 90% efficient, meaning that 90% of the energy supplied to it ends up as mechanical work.

If the motor lifts a 210 weight at 3.5 , how much current does it draw?

Express your answer using two significant figures.

I= ? Amps

- Physics 8B -
**Henry**, Tuesday, September 20, 2011 at 7:12am
No units are given; therefore, I'll have to make some assumptions:

Wt = 210 Newtons @ 3.5m/s.

280 Volt motor

Power = 210 * 3.5m/s = 735 Watts output

Power Input = Po / 0.9 = 735/0.9 = 817

Watts.

P = V*I,

I = P / V = 817 / 280 = 2.9 Amps.

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