Non-consecutive forces with block and string

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Homework Help Overview

The problem involves a 4-kg block attached to a 2 m string, rotating on a horizontal surface, with a focus on calculating the work done by the force of friction during each revolution. The coefficient of friction is given as 0.25.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to calculate the work done by friction using the coefficient of friction and the weight of the block, but struggles with determining the distance traveled around the circle. A participant questions the setup regarding the attachment of the string to the center of the circle.

Discussion Status

Some clarification has been provided regarding the setup of the block and string, which seems to have helped the original poster understand the situation better. However, there is no explicit consensus on the calculations or the approach to finding the distance around the circle.

Contextual Notes

The original poster mentions an answer of -123 J, but it is unclear how this value was derived given the uncertainties in the problem setup and calculations.

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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