A 7.5-kg otter slides down a hill, starting from rest at the top. The sloping surface of the hill is 8.8 m long, and the top is 6.5 m above the base.

a) Find the speed of the otter at the bottom of the hill (assume there is no friction).

Now assume there is friction. b) If the speed of the otter at the bottom of the hill is 9.2 m/s, how much energy was lost to friction? c) Find the magnitude of the force of friction.