# Chapter 8 - Friction - Section 8.2 - Problems Involving Dry Friction - Fundamental Problems - Page 417: 9

$16.67N$

#### Work Step by Step

We know that when Block B starts moving, then $P-\mu g=0$ We plug in the known values to obtain: $P-0.3(10)(9.81)=0$ $\implies P=294N$ When Block B starts rotating about P, then $\Sigma M_P=0$ $\implies 10\times 9.81\times 0.15-P\times 0.40=0$ $\implies P=36.8N$ Similarly, when A starts moving, then $P-(0.1)(17\times 9.81)=0$ $\implies P=16.67N$ This is the required force which is applied to the cord without causing motion.

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