More Fluids

1. Nov 3, 2006

Forceflow

In Figure 14-31, an open tube of length L = 1.8 m and cross-sectional area A = 4.6 cm2 is fixed to the top of a cylindrical barrel of diameter D = 1.2 m and height H = 1.8 m. The barrel and tube are filled with water (to the top of the tube). Calculate the ratio of the hydrostatic force on the bottom of the barrel to the gravitational force on the water contained in the barrel.
Why is that ratio not equal to 1.0? (You need not consider the atmospheric pressure.)

I calculated the ratio and the ratio is 2. However, i have no clue to why that ratio wouldn't be equal to one.

2. Nov 4, 2006

Andrew Mason

Why not show us what you did.

The gravitational force on the water contained in the barrel is the weight of the water in the barrel, which is equal to its mass x gravitational acceleration: Mg.

The hydrostatic force on the bottom of the barrel is equal to the weight of the water above it: weight of water in both tube and barrel.

So the ratio is M/(M+m) where M is the mass of the barrel and m is the mass of the water in the tube. That should be 100/(100+1)

AM