How Is Work Done by Friction Calculated on a Quarter Circle Ramp?

[Jtappan]

Homework Statement

Jim rides his skateboard down a ramp that is in the shape of a quarter circle with a radius of 6.50 m. At the bottom of the ramp, Jim is moving at 2.82 m/s. Jim and his skateboard have a mass of 67.0 kg. How much work is done by friction as the skateboard goes down the ramp?
______J

Homework Equations

angular velocity? + frictional force equation?

The Attempt at a Solution

How is the frictional force determined from this without the kinetic friction coefficient?

 

[G01]

In this case you do not actually need the force of friction to find the work done by it.

HINT: Think in terms of conservation of energy. What can this principle tell you about this problem?