# Equilibrium Problem

Summation F(x)=0

Summation F(y)=0

Summation tau=0

## The Attempt at a Solution

I know how to calculate the problem but I don't know the last part of the solution why the examinar choose mu(min)=1. Please help me.Thank you.

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kuruman
Homework Helper
Gold Member
You have already seen that the force of friction is the same 4N at all points. That's what's required to keep the system at equilibrium. Imagine starting with a large μ and reducing it gradually. Slipping will occur at the point where the maximum value that static friction can have (=μ R) goes just below the value 4 N first. So if you write

μR = 4 N,

at which of the three points A, B and C μR falls below 4 N first as you make μ smaller?

You have already seen that the force of friction is the same 4N at all points. That's what's required to keep the system at equilibrium. Imagine starting with a large μ and reducing it gradually. Slipping will occur at the point where the maximum value that static friction can have (=μ R) goes just below the value 4 N first. So if you write

μR = 4 N,

at which of the three points A, B and C μR falls below 4 N first as you make μ smaller?

Thank you very much for explaination.Firstly I don't understand so I read many times your concept. Now I understand. I really appreciate you. Sorry for replying late.