# Non-consecutive forces with block and string

1. May 13, 2014

### BrainMan

1. The problem statement, all variables and given/known data
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.

2. Relevant equations
Wnc= (KEf-KEi)+ (PEf-PEi)
KEi+PEi=KEf+PEf

3. 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

2. May 13, 2014

### paisiello2

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

3. May 14, 2014

### BrainMan

I'm not sure

4. May 14, 2014

### BrainMan

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