Lisa runs up 4 flights of stairs in 22. seconds. She weighs 510. Newtons. If eac

Question

Lisa runs up 4 flights of stairs in 22. seconds. She weighs 510. Newtons. If each flight rises 310. cm:

(a) What is her change in potential?
(b) What average power (watts) was required during the 22. s?
(c) What minimum horsepower motor would be required to do this?

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I need help with this.

Please, don't answer it unless you're going to explain every single step and equation you use, as clearly as possible.

I would, for sure, give full Karama Points to a clearly-explained, and fully-described answer.

Thanks.

Explanation / Answer

Given Weight of lisa   W = mg = 510 N Heigth of 4 stairs   h = 4 flights                                 = ( 4 flights ) ( 310 cm / 1 flight )                                 = 4 ( 310 cm ) ( 0.01 m / 1 cm )                                 = 12.4 m a) Change in potential energy is                   P.E = m g h                          = ( 510 N ) ( 12.4 m )                          = 6324 J ________________________________________________ b) power required during the time                P = Work / time                    = ( 6324 J ) / ( 22 s )                    = 287.4545 W _______________________________________________ c) 1 horse power 1 hp = 745.699 W Required minimum horse power                 287.4545 / 745.699 =   0.385 hp     

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