Find minimum normal force to be each hand to hold there identical books in verticle position Each books has mass `m` and the value of coefficient of friction between the books as well as between hand and the book is `mu`

Explanation

From FBD for center book `2f_(1) = mg`

`f le mu N rArr mu N gt (mg)/(2)`
` N gt (mg)/(2 mu)`…(i)
For side book `f - f_(1) = mg`
` f = (3mg)/(2) le mu N`
` N ge (3mg)/(2 mu)`…(ii)
By Eqs (i) and (ii)
Thus, minimum `N = (3mg)/(2 mu)`