Finding friction force?

Question

A 68.5 skater moving initially at 2.40 on rough horizontal ice comes to rest uniformly in 3.52 due to friction from the ice.

What is the friction force?

Answer 1

You can look at work done to solve this

The work done by the frictional force, f, is
f*d, or f*3.52
The initial kinetic energy of the skater is
.5*68.5*2.4^2
since Ice is level
f=.5*68.5*2.4^2/3.52
or 56.0 N

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