Suppose you are testing a new amusement park roller coaster with an empty car with a mass of 100 kg. One part of the track is a vertical loop with a radius of 12.0 m. At the bottom of the loop (point A), the car has a speed of 25.0 m/s and at the top of the loop (point B), it has a speed of 8.00 m/s. As the car rolls from point A to point B, how much work is done by friction? Use 9.81 m/s2 for the acceleration due to gravity.

Explanation:

Gain  of kinetic energy + work done by friction = loss of potential energy

= 1 / 2 m ( 25² - 8² ) + work done by friction = m x 9.8 x ( 12 + 12 )

= .5 x 100 x ( 625 - 64 ) + work done by friction = 100 x 9.8 x 24

28050 + work done by friction = 23520

work done by friction = -4530 J

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