A liquid is kept in a glass beaker. Which one of the following statements is correct regarding the pressure exerted by the liquid column at the base of the beaker ?
- A.The pressure depends on the area of the base of the beaker
- B.The pressure depends on the height of liquid column
- C.The pressure does not depend on the density of the liquid
- D.The pressure neither depends on the area of the base of the beaker nor on the height of liquid column
Correct answer
Explanation
The correct answer is B, the pressure depends on the height of liquid column. Liquid pressure at a depth is P = hρg, so a taller column presses harder on the base.
In P = hρg, h is the height of the liquid above the point, ρ is the density of the liquid and g is the acceleration due to gravity. The area of the base does not appear: a wide beaker holds more liquid and a heavier load, but that load is spread over a larger area, so the pressure stays the same for the same height. This is why water tanks are placed high and why dams are built thicker at the bottom.
A is wrong because pressure at the base is independent of the base area.
C is wrong because pressure is directly proportional to the density of the liquid.
D is wrong because pressure clearly rises with the height of the column.
Exam tip: P = hρg; liquid pressure depends on depth and density, never on the shape or base area of the vessel.
Practice Questions
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