A roller coaster starts from rest at the top of an 18-m hill as shown. The car t

Question

A roller coaster starts from rest at the top of an 18-m hill as shown. The car travels to the bottom of the hill and continues up the next hill that is 10.0 m high. a. How fast is the car moving at the top of the 10.0-m hill, if friction is ignored? b. how fast is the car moving at the flat portion of the ride, if friction is ignored? c. Because in the real world friction DOES exist consider the following.....If friction on the track now does -1500 J of work on the cart that has a mass of 150 kg. Calculate the velocity of the cart at the flat portion of the ride.

Explanation / Answer

(A) Applying energy conservation,

PEi + KEi = PEf + KEf

m g (18) + 0 = m g (10) + m v^2 /2

v^2 = 2 x 9.8 x (18 - 10)

v = 12.52 m/s

(b) PEi + KEi = PEf + KE f

m g (18) + 0 = 0 + m v^2 /2

v = sqrt(2 x 9.8 x 18) = 18.8 m/s

(c) [(150 x 9.8 x 18) + 0 ] - 1500 = 0 + 150 v^2 /2

24960 = 150 v^2 / 2

v = 18.24 m/s

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