Fluids Physics Question: Calculating Density and Pressure of a Physics Book"

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Homework Statement


A physics book has a height of 26.0 cm, a width of 22.4 cm, and a thickness of 3.10 cm.

(a) What is the density of the physics book if it weighs 18 N?
? kg/m3
(b) Find the pressure that the physics book exerts on a desktop when the book lies face up.
? Pa
(c) Find the pressure that the physics book exerts on the surface of a desktop when the book is balanced on its spine.
? Pa


Homework Equations



Divide the weight by gravity to get the mass.
18N/9.81 = 1.83 kg.
P = F/A

The Attempt at a Solution



Convert cm to meters:
(26.0cm)/100 = 0.26
22.4/100 = 0.224
3.10/100 = 0.031
Now divide
1.83/(0.26*0.224*0.031) = 1.83/0.00180544 = 1014 kg/m^3
P = F/A
area of the book = (0.224*0.26) = 0.5824 m^2
18/0.5824 = 30.9 Pa

When balanced on its spine, its width and thickness make up the area
(0.224*0.0310) = 0.006944
18/0.006944 = 2592 Pa
 

Discussion

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You got the first two right, but I would say that you should use height in the last problem instead of width.
 
Like i said, I believe my answer is wrong. If someone would double check it.
 
That's what I'm saying. Your answer is wrong because you used the wrong number in your calculations. All you need to do is use the right one.