An electrical resistance inputs the same amount of energy into a fluid as does a paddle wheel. How long should a 20-? electrical resistance operate across a potential of 12 V to produce the same work as a 50-kg mass attached to the paddle wheel that falls a distance of 2 m?

A) 67 s
B) 84 s
C) 119 s
D) 136 s


D) 136 s

The work input by the paddle wheel is mgh and that by an electrical resistance is Vi t. Using

i = V / R, the relationship takes the form



If the mass is in kg, gravity is in m/s2, h is in m, V is in volts, R is in ohms, ?t will be in seconds.

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What will be an ideal response?

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