A skateboard track has the form of a circular arc with a 3.75 m radius. A 47.0 kg skateboarder starts from rest at the top of the circular arc. What is the normal force exerted on the skateboarder at the bottom of the circular arc? I tried using conservation of energy to solve for v mgh=1/2 mv^2 and then I tried plugging that in for F=mv^2/r but it didn't work. How are you supposed to do this problem?