Quesiton: You are testing a new amusement park roller coaster with an empty car with a mass of 108kg. One part of the track is a vertical loop with a radius of 12.0m. At the bottom of the loop (pointA) the car has a speed of 25.0m/sand at the top of the loop (pointB) it has speed of 8.00m/s.
As the car rolls from point A to point B, how much work is done by friction?