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Using the method of composite bodies, find the centroid of the shape shown. Show

ID: 1720993 • Letter: U

Question

Using the method of composite bodies, find the centroid of the shape shown. Show the centroid on the shape provided. A superman cyclist rode a bike uphill at 20 miles/hour for two hours. To sustain this constant speed the cyclist was exerting 50 pounds, (a) How much work has the cyclist done during the trip? How many power bars arc needed to make up for the lost energy? Assume that one power bar has 300kcal and that a fit person's energy conversion efficiency is 25%. Google the the needed conversion formulas.

Explanation / Answer

1.

Distance travelled uphill,d =speed*time=20*2=40 miles=21200 feet

(a)

Force exerted was ,F=50 pounds

Hence work done,W=F*d=50*21200=10560000 ft-pound~ 3419.66 kcal

One power bar has 300 kcal but body has 25% efficiency hence only 25% of 300 kcal can be used.

Hence number of powerbars needed = 3419.66/(300*0.25)=45.59~46 powerbars