Suppose the skateboarder shown in the drawing reaches a height of 1.60 m above the right side of the semicircular ramp. He then makes an incomplete midairturn and ends up sliding down the right side of the ramp on his back. When the skateboarder reaches the bottom of the ramp, his speed is 6.50 m/s' The skateboarder's mass is 67.0 kg, and the radius of the semicircular ramp is 2.10 m.What is the average frictional force exerted on the skateboarder by the ramp