Physics 8B

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

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  1. 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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