Question

Difficulty: EasyHydrostatic Pressure

A cylindrical water storage tank is filled to a depth of 4 meters4\text{ meters}, creating a hydrostatic pressure of 40,000 Pascals40,000\text{ Pascals} at the tank's flat bottom. If water is drained from the tank until the depth is exactly 1 meter1\text{ meter}, what is the new hydrostatic pressure at the bottom in Pascals? (Assume the density of water and gravity remain constant.)

Answer: 10000 Pascals

Answer

10000
Because hydrostatic pressure is directly proportional to depth (P=ρghP = \rho g h), reducing the depth to one-fourth of its original value (1 meter1\text{ meter} instead of 4 meters4\text{ meters}) also reduces the pressure exactly to one-fourth of its original value (40,000/4=10,00040,000 / 4 = 10,000).

Step-by-Step Solution

1
Identify the relationship between hydrostatic pressure and fluid depth.
Hydrostatic pressure is directly proportional to depth (P∝hP \propto h) when density and gravity are constant.
This fundamental principle allows us to solve the problem using a simple ratio.
2
Calculate the pressure per unit of depth.
40,000 Pascals4 meters=10,000 Pascals per meter\frac{40,000\text{ Pascals}}{4\text{ meters}} = 10,000\text{ Pascals per meter}.
Finding the rate of pressure change per meter simplifies the calculation for the new depth.
3
Multiply the pressure per meter by the new depth.
10,000 Pascals/meter×1 meter=10,000 Pascals10,000\text{ Pascals/meter} \times 1\text{ meter} = 10,000\text{ Pascals}.
This yields the final pressure at the reduced depth.

Key Concept

Hydrostatic pressure is directly proportional to the depth of the fluid.
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