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Mechanical Properties of Fluids is one of the most reliable scoring chapters in NEET(UG) Physics. Pressure, floating, flow, viscosity and surface tension — five small topics, each with two or three formulas, and the paper picks from them almost every year. The mistakes students make here are small ones: forgetting that a soap bubble has two surfaces, or that a floating body sinks only as deep as its own density says. Ten questions below. Give them ten honest minutes.
What this chapter carries in NEET(UG)
- Usually 2 to 3 questions every year, which is 8 to 12 marks.
- Surface tension and the excess pressure formulas are asked nearly every year.
- Bernoulli, terminal velocity and floating bodies share the rest.
What the syllabus says
In the syllabus (Unit 7, Properties of Solids and Liquids): Pressure due to a fluid column, Pascal’s law and its applications, the effect of gravity on fluid pressure, viscosity, Stokes’ law, terminal velocity, streamline and turbulent flow, critical velocity, Bernoulli’s principle and its applications, surface energy and surface tension, angle of contact, excess pressure across a curved surface, and surface tension applied to drops, bubbles and capillary rise.
Taken out in 2024: Reynolds number.
Taken from the NMC syllabus for NEET (UG) 2026, the latest one published. See the full syllabus, unit by unit.
Formulas you must know by heart
| Pressure at a depth | P = P0 + ρgh |
| Pascal’s law, hydraulic lift | F1/A1 = F2/A2 |
| Upthrust | F = Vρg |
| Floating body | fraction submerged = ρbody / ρliquid |
| Equation of continuity | A1v1 = A2v2 |
| Bernoulli’s equation | P + ½ρv2 + ρgh = constant |
| Speed of efflux | v = √(2gh) |
| Stokes law | F = 6πηrv |
| Terminal velocity | v = 2r2(ρ − σ)g / 9η |
| Excess pressure | drop 2T/R, soap bubble 4T/R |
| Capillary rise | h = 2T cosθ / rρg |
The difference between 2T/R and 4T/R is only this: a liquid drop has one surface, a soap bubble has two, an inside one and an outside one. Every year a few students lose a mark by using the wrong one.
Ten questions. Give yourself ten minutes.
Write your answers down before you scroll. A question you looked up is a question you have not answered.
Q1. The gauge pressure at a depth of 10 m in water (ρ = 1000 kg/m3, g = 10 m/s2) is
- (a) 103 Pa
- (b) 104 Pa
- (c) 105 Pa
- (d) 106 Pa
Q2. In a hydraulic lift the areas of the two pistons are in the ratio 1 : 50. A force of 100 N on the small piston can lift a load of
- (a) 50 N
- (b) 500 N
- (c) 5000 N
- (d) 2 N
Q3. A block floats in water with one quarter of its volume above the surface. Its density is
- (a) 250 kg/m3
- (b) 500 kg/m3
- (c) 750 kg/m3
- (d) 1000 kg/m3
Q4. The terminal velocity of a small sphere falling through a viscous liquid is proportional to
- (a) r
- (b) r2
- (c) 1/r
- (d) r3
Q5. Water flows through a pipe whose radius narrows to half. The speed of the water there becomes
- (a) half
- (b) double
- (c) four times
- (d) unchanged
Q6. Bernoulli’s theorem is a statement of the conservation of
- (a) mass
- (b) momentum
- (c) energy
- (d) angular momentum
Q7. The excess pressure inside a soap bubble of radius R, for a liquid of surface tension T, is
- (a) 2T/R
- (b) 4T/R
- (c) T/R
- (d) T/2R
Q8. If the radius of a capillary tube is doubled, the height to which water rises in it
- (a) doubles
- (b) becomes half
- (c) stays the same
- (d) becomes four times
Q9. The angle of contact between water and clean glass is close to
- (a) 0°
- (b) 90°
- (c) 135°
- (d) 180°
Q10. The SI unit of the coefficient of viscosity is
- (a) N/m2
- (b) N·s/m2
- (c) N·m
- (d) N/s
Answer key, with a hint for each
| Q1 | (c) | Gauge pressure is ρgh = 1000 × 10 × 10. |
| Q2 | (c) | Pressure is the same on both pistons, so force scales with area: 100 × 50. |
| Q3 | (c) | Three quarters is submerged, so the density is three quarters of 1000. |
| Q4 | (b) | In the terminal velocity formula the radius appears squared. Weight grows as r3, drag only as r, so the balance leaves r2. |
| Q5 | (c) | Area goes as r2, so halving the radius quarters the area. By Av = constant the speed must become four times. |
| Q6 | (c) | It is the work–energy theorem written for a flowing fluid, with a pressure term, a kinetic term and a height term. |
| Q7 | (b) | A soap bubble has two surfaces. A single drop would give 2T/R. |
| Q8 | (b) | h is proportional to 1/r. Wider tube, smaller rise. |
| Q9 | (a) | Water wets clean glass almost completely, so the angle of contact is near zero. That is why it rises in a capillary. |
| Q10 | (b) | From F = ηA(dv/dx), η works out to N·s/m2, also called the pascal second. |
Now mark yourself honestly
NEET(UG) marks the way it marks. Use the same rule here:
- +4 for a right answer
- −1 for a wrong one
- 0 for a blank
So ten questions here are out of 40. In the real paper, 45 Physics questions are out of 180.
If you scored 32 or more, the basics of this chapter are secure. Move to harder questions, not more of these.
If you scored below 24, do not feel bad about it. You have just found out something useful before the exam did. Go back to the formula table above, learn it properly, and sit these ten again tomorrow.
And if you guessed a few and they landed, count those as wrong. A guess that works once will not work in May.
The full chapter, on a clock
Ten questions tell you a little. Forty-five tell you the truth.
The Beginner paper for Mechanical Properties of Fluids is waiting for you on the portal: 45 questions, 45 minutes, marked out of 180, with the answer key and a hint for every question. Sit it tonight and you will know exactly where this chapter stands.
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