Calculating Coefficient of Kinetic Friction from Given Forces

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Homework Help Overview

The problem involves calculating the coefficient of kinetic friction for a block on a horizontal surface, given the forces required to initiate and maintain motion. The subject area is physics, specifically focusing on friction and forces.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the forces acting on the block, questioning the interpretation of the forces required to overcome static and kinetic friction. There is debate over the correct application of these forces in calculations.

Discussion Status

Participants are exploring different interpretations of the forces involved. Some have offered guidance on how to approach the calculations, while others are questioning the assumptions made regarding the friction forces.

Contextual Notes

There is a lack of clarity regarding the distinction between static and kinetic friction forces, and how they relate to the forces provided in the problem. The original poster expresses uncertainty about their calculations and the reasoning behind them.

Ry122
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A 23.0 kg block is initially at rest on a horizontal surface. A horizontal force of 76.0 N is required to set the block in motion. After it is in motion, a horizontal force of 60.0 N is required to keep the block moving with constant speed. Find the coefficients kinetic friction from this information.

my attempt:
After the block is in motion 60N is required to prevent it from accelerating.
Therefore what is left over must be used to overcome friction which is 16N.
Friction force = weight x coefficient of kinetic friction
16N=23x9.8 x ck
ck=.070
But this is incorrect.
What am i doing wrong?
 
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60N is the force required to prevent it from accelerating, this is the same force to overcome friction. 16N isn't anything in this problem, it's just the difference between the force required to overcome static friction and the force required to overcome kinetic friction.

Replace 16N with 60N in your calculations and try again.
 
When friction force and the accelerative force are equal speed is constant. Anything extra will cause the body to accelerate so the accelerative force isn't overcoming friction.
60n is used to determine the static friction.
 
as you say you need the same force as friction to stay at constant velocity.

The question tells you there there is 60 N of friction when moving.

76 N is used to determine static friction.
 

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