# physics

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A 120-V motor has mechanical power output of 3.20 hp. It is 81.0% efficient in converting power that it takes in by electrical transmission into mechanical power.
(a) Find the current in the motor.
(b) Find the energy delivered to the motor by electrical transmission in 3.60 h of operation.
?J
(c) If the electric company charges \$0.160/kWh, what does it cost to run the motor for 3.60 h?
\$

• physics -

(b) Output power = 3.20 hp = 2387 Watts
Input power = 2387/0.81 = 2947 W

Electrical energy delivered in 3.60 h
= 2947 J/s*3.2 h*3600 s/h = 3.395*10^7 J

(c) 2.947 kW*3.2 h = ___ kWh
Multiply that by the cost per kWh

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