Physics 1205
Assignment #8



Problem A: You are watching a friend of yours compete in a skateboard competition. The skateboard track is horizontal and flat on the bottom and then arcs up in the shape of a quarter-circle with radius of 5.0 meters, so that the track is vertical at the top of the quarter-circle. Your friend does a trick where he rides his skateboard along the flat section then continues up the arc to the top of the quarter-circle ramp. He stops momentarily at the top of the arc, then turns around and comes back down the quarter-circle ramp. An official sitting next to you is using a radar gun to measure the speed of the skaters and you notice that at the bottom of the quarter-circle ramp your friend is traveling 9.0 m/s. You know your friend has a mass of 75 kg. You begin to wonder what frictional force is exerted on your friend's skateboard. You realize the you have enough information to figure this out so you calculate the work done by friction on the skateboard and the average frictional force on the skateboard.