Posted by JL on .
A Physics book has a height of 26 cm, a width of 22 cm, and a thickness of 4 cm.
Find the pressure that the Physics book exerts on a desktop when the book lies face up and when the book is balanced on its spine.
I know that P=F/A, I am just not sure which dimensions of the book to use for area. Initially, I used P=density*g*height and got it wrong. I used .26 m for the height, so I think that I used the wrong value for height.

AP Physics 
drwls,
Face up, the area in contact with the desktop is 26 x 22 cm^2.
On the "spine" (binding, where the title is embossed, the area is 26 x 4 cm^2.
You are correct that the density (or weight) of the book will be needed, and pressure = F/A. The weight is M g or (density)*g*volume