Physics Help Forum Book friction problem
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 Oct 22nd 2017, 09:53 AM #1 Junior Member   Join Date: Oct 2017 Posts: 8 Book friction problem Problem Suppose you are holding a heavy physics book upright between your hands as shown in the figure to the right. The mass of the book is 4.00 kg. When your right hand applies a force of 50.0 N normal to the book as shown, the book remains at rest. b.)What is the minimum possible value of the coefficient of static friction between your hands and the book? Assume the coefficient of static friction between your left hand and the book is the same as the coefficient of static friction between your right hand and the book. Known information n1=50N m=4.00kg Fnet=0 Free Body Diagram Attempt at a solution $\displaystyle x:n2-n1=0 (1)$ $\displaystyle y:Fs1+Fs1-mg=0 (2)$ $\displaystyle Fs≤µsn (3)$ $\displaystyle (1) =>n2=n1=50N$ $\displaystyle (3) =>Fs=µ(50)$ $\displaystyle (2) => 100µ=mg$ $\displaystyle (2) => µs=(4*9.80)/100$ $\displaystyle (2) => µs=.392$ The concept I'm wondering about is the minimum value of the coefficient of static friction. Was I right to set Fs=µn after I had figured out that the normal forces are the same in magnitude? If not I'm not really sure how to go about this.
 Oct 22nd 2017, 11:34 AM #2 Senior Member   Join Date: Apr 2015 Location: Somerset, England Posts: 1,035 Your approach is generally correct.

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