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You arc designing a new roller-coaster. The main feature of this particular desi

ID: 1483497 • Letter: Y

Question

You arc designing a new roller-coaster. The main feature of this particular design is to be a vertical circular loop-the-loop where riders will feel like they are being squished into their seats even when they are in fact upside-down (at the top of the loop). The coaster, mass 1000 kg, starts at rest a height of 80 m above the ground, speeds up as it descends to ground level, and then enters the loop which has a radius of 20 m. Suppose a rider is sitting on a bathroom scale that initially reads 980 N =W (when the coaster is horizontal and at rest). What will the scale read when the coaster is moving past the top of the loop? (You can assume the (he coaster rolls on (he track without friction) what is the final velocity, Vf at the top of theloop?

Explanation / Answer

a)

By Conservation of energy

KEi+PEi =KEf+PEf

(1/2)mVi2+mgYinitial = (1/2)mVf2+mg(2R)

gYinitial=(1/2)Vf2+2gR

Vf2 =2[gYinitial-2gR] =2[9.8*80-2*9.8*20

Vf=28 m/s

Centripetal force

Fc=mVf2/R =1000*282/20

FC=39200 N

At the top of the loop net force is given by

Fnet=W+FN

So Normal Force

FN=FNet-W =39200-9800

FN=29400 N

b)

final velocity at the top of the loop is

Vf=28 m/s