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An electric motor has a rating of 4.0 × 10^2 watts.

How much time will it take for this motor to lift a

50.-kilogram mass a vertical distance of 8.0 meters?

[Assume 100% efficiency.]

(1) 0.98 s (3) 98 s

(2) 9.8 s (4) 980 s

Verified Answer :

The energy expended during move can be calculated using the Definition of Work, that is given by:

\(E=P\Delta S\)
 
     Using the Definition of Potence, comes:

\(P_{ot}= \frac{P}{\Delta t} \\ \Delta t = \frac{P\Delta S}{P_{ot}}\)
 
     Entering the unknowns, we have:

\(\Delta t = \frac{P\Delta S}{P_{ot}} \\ \Delta t = \frac{50*9.8*8}{4*10^2} \\ \boxed {\Delta t =9.8s}\)

Number 2

If you notice any mistake in my english, please let me know, because i am not native.

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