Answer
a. Yes.
b. No.
Work Step by Step
a. Yes, the work done by friction can be determined. Three forces act on the coaster: gravity, the normal force from the track, and friction. The work done by gravity is the negative of the change in potential energy. The normal force does no work because it is perpendicular to the car’s motion.
Friction is the only other force acting on the coaster. The work done by friction is the change in the car’s mechanical energy between the initial and final positions, and will be a negative amount of work.
b. No, the average force of friction depends on how long the car’s path is. To find the average force of friction, we would need to know the total distance traveled by the car.