Water Pressure
Classical Mechanics
Level
2
The water pressure driving water through the generator in a dam depends on
the surface area of the dam that is in contact with the lake
the depth below the surface at which the outlet is located
the horizontal distance from the dam at which the outlet is located
the volume of lake water held back by the dam
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1 solution
The pressure in a body of still water only depends on the height of water column above it. If the pressure at the surface of the water is P 0 , then the pressure at depth d below the surface is P = P 0 + ρ g d .
We see that pressure depends only on the depth. It does not depend on the surface area of the dam, volume of water, or horizontal distance from the dam. The pressure does not change if we measure at different points at the same depth.
If we go deeper in the water, then the pressure increases. This is why the thickness of the dam increases as we go down; the dam needs to be able to withstand greater pressure at the bottom as compared to the top.