In the figure, a frictionless roller coaster car of mass m = 990 kg tops the fir

Question

In the figure, a frictionless roller coaster car of mass m = 990 kg tops the first hill with speed v_o = 18.4 m/s at height h = 38.1 m. How much work does the gravitational force do on the car from that point to (a) point A, (b) point 8, and (c) point C? If the gravitational potential energy of the car-Earth system is taken to be zero at C, what is its value when the car is at (d) B and (e) A? Number ____________ Units Number ____________ Units Number _________ Units Number _______________ Units Number _____________ Units

Explanation / Answer

W = mgh. (m = mass, g = gravity and h = height)
m= 990kg
g= 9.81 m/s²
h= 38.1m

a) Point A

W = mg(h-h) = (990)(9.8)(38.1-38.1)= 0
W=0 J

b) Point B

W = mg(h - h/2) = (990)(9.8)(38.1-(38.1/2))= 185011.695 = 1.85e5
W = 1.85e5 J

c) Point C

W= mgh = (990)(9.8)(38.1) = 370023 = 3.70e5
W = 3.70e5 J

PE = mgh

d) Pe = mgh/2 = [(990)(9.8)(38.1)]/2 = 185011 = 1.85e5
Pe = 1.85e5 J

e) Pe = mgh = (990)(9.8)(38.1) = 370023 = 3.70e5
Pe = 3.70e5 J

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