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Foundation3 past questions

Pressure in fluids and hydrostatics

Explores how pressure is transmitted in fluids, including hydrostatic pressure, Pascal's law, and related phenomena.

Why this shows up in the exam

You need to apply these principles to solve problems involving fluids at rest and pressure transmission in NEET.

How NEET tests this

Numerical · 2 QsStatement analysis

Learn the idea

In a fluid at rest the pressure at any depth depends only on the height of the liquid column above that point, not on the shape or volume of the container. This single insight – P = ρgh – unlocks every hydrostatic problem.

🧠 Memory hook: Depth decides pressure – ‘Height gives the h in ρgh, not the shape of the pot’

Get this one clearly and it pays off every single time it shows up in the paper. 🎯

Formulas & facts to keep ready

  • Hydrostatic pressure: P = ρ g h (add atmospheric pressure if the surface is open)
  • ρ = mass/volume of the fluid (kg m⁻³)
  • Pressure at a point in a static fluid is same in all directions (isotropic)
  • Pascal’s law: any change in pressure applied to a confined fluid is transmitted undiminished throughout the fluid
  • For a horizontal base, pressure is uniform over the whole area
  • Force on a surface = pressure × area

How to approach it

  1. 1Read the question and note the fluid, its density and the vertical height of the column
  2. 2Write P = ρ g h (include P₀ if the surface is exposed to atmosphere)
  3. 3If asked for force, multiply the pressure by the given area
  4. 4Use Pascal’s law when the problem involves pressure transmission to another part of the fluid

Worked example — watch it click

Two copper vessels A and B have the same base area but different shapes. A takes twice the volume of water as that B requires to fill upto a particular common height. Then the correct statement among the following is:

  • ✅Pressure on the base area of vessels A and B is the same.
  • B)Pressure on the base area of vessels A and B is not the same.
  • C)Both vessels A and B weigh the same.
  • D)Vessel B weighs twice that of A.

The concept behind this problem

The example checks whether you know that hydrostatic pressure at the base is governed solely by the common liquid height, irrespective of how much water each vessel holds.

Step by step

  1. 1Pressure at the base depends only on height of liquid column: P = P₀ + ρgh.
  2. 2Since both vessels are filled to the same height h with the same liquid, the pressure at the base is identical regardless of vessel shape or volume.

Watch out

Students often think the vessel that holds more water exerts a larger pressure on its base, overlooking that pressure depends only on height.

Common slip-ups that cost marks

  • •Forgetting to add atmospheric pressure when the liquid surface is open
  • •Confusing total volume of liquid with pressure – volume does not appear in P = ρgh
  • •Assuming the shape of the vessel changes the pressure at the base

🌟 That's the whole idea — you've got this. Try the practice set below; every question you attempt makes it stick a little harder.

Practise it

These are real questions from past NEET papers that test this exact idea.

Question 1 of 3NEET 2022

Two copper vessels A and B have the same base area but different shapes. A takes twice the volume of water as that B requires to fill upto a particular common height. Then the correct statement among the following is:

Push further

More challenging

8 harder questions built from the past papers above — a step up in difficulty, with distractors designed so you can't get there by elimination. Written and checked by our reviewers, not from a real paper.

Question 1 of 8

Two containers, one cylindrical and one conical, both have the same base area of 0.1 m² and are filled with water to a height of 0.5 m. What is the pressure exerted by the water on the base of each container? (Density of water = 1000 kg/m³, g = 10 m/s²)

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