Non-consecutive forces with block and string

AI Thread Summary
The discussion revolves around calculating the work done by friction on a 4-kg block attached to a 2 m string rotating on a horizontal surface, with a friction coefficient of 0.25. The user attempted to find the work done by multiplying the friction coefficient by the block's weight and the total distance traveled in a circle but struggled to determine the circular distance. The correct answer for the work done by friction was identified as -123 J. Clarification was sought regarding whether the string is fixed at the center of the circle. The conversation highlights the importance of understanding the relationship between friction, weight, and circular motion in physics problems.
BrainMan
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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
 
Physics news on Phys.org
Is the block tied to a string that is pinned to the circle's center?
 
I'm not sure
 
It works that way so I get it now. Thanks!
 

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