June 2010 Physics Regent Discussion?

the pendulum lost potential energy because that energy that's gone turns into internal energy. for the part b or c one with the the ice skater and they give you the kinetic coefficient of friction. for finding the force that was pulling i used the accelartion they gave me. but to find the force of gravity (so you could use the normal forcce to plug into the friction equation), i used 9.81 because it seemed silly to have 28N pulling it and 28 N as force of gravity too.