A woman holds a book by placing it between her hands such that she presses at right angles to the front and back covers. The book has a mass of m = 1.3 kg and the coefficient of static friction between her hand and the book is μs = 0.69. What is the weight of the book in Newton?

Explanation:

In order to solve this problem we need to make a free body diagram of the book and the forces that interact on it. In the picture below you can see the free body diagram with these forces.

The person holding the book is compressing it with his hands, thus exerting a couple of forces of equal magnitude and opposite direction with value F.

Now the key to solving this problem is to analyze the equilibrium condition (Newton's third law) on the x & y axes.

To find the weight of the book we simply multiply the mass of the book by gravity.

W = m*g

W = 1.3[kg] * 9.81[m/s^2]

W = 12.75 [N]

f is prop to m1xm2 double m1 double force