Non-consecutive forces with block and string

[BrainMan]

Homework Statement

a 4-kg block is attached to a string 2 m in length rotates on a horizontal surface. (a) If the co-efficient of friction between the block and the surface is .25, find the work done by the force of friction in each revolution of the block.

Homework Equations

Wnc= (KEf-KEi)+ (PEf-PEi)
KEi+PEi=KEf+PEf

The Attempt at a Solution

I attempted to find the work done by friction by multiplying the co-efficient of friction by the weight of the object and then multiplying that by the total distance around the circle. Unfortunately I couldn't find the distance around the circle based on the information provided. The answer to this problem was -123 J

 

[paisiello2]

Is the block tied to a string that is pinned to the circle's center?

 

[BrainMan]

I'm not sure

 

[BrainMan]

It works that way so I get it now. Thanks!