Question

You need to lift a 100 lbmrock 300ft with an electric motor that is 60% efficient, how much will it cost if the electricity is 10 cents per kWh?

Answer 1

0.066 cent

Step-by-step explanation:

Efficiency (E) = Energy output (Eo)/Energy input (Ei)

Eo = E × Ei

E = 0.6

Ei = mass × acceleration due to gravity × height

mass = 100lbm = 100×0.45359kg = 45.359kg, height = 300ft = 300/3.2808 = 91.44m

Ei = 45.359×9.8×91.44 = 40646.7Ws = 40.6467kWs = 40.6467kWs × 1h/3600s = 0.011kWh

Eo = 0.6 × 0.011kWh = 0.0066kWh

1kWh = 10 cents

0.0066kWh = 0.0066×10 = 0.066 cent