A52.0 kg skateboarder does a trick on a half-pipe. during the trick, he reaches a speed of 8.90 m/s. the radius of the half-pipe ramp is 3.00 meters. what is the minimum centripetal force necessary to keep the skater on the ramp?

A1-lb collar is attached to a spring and slides without friction along a circular rod in a vertical plane. the spring has an undeformed length of 5 in. and a constant k =25 lb/ft. knowing that the collar is released from being held at a determine, the speed of the collar and the normal force between the collar and the rod as the collar passes through b.