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Mechanical Properties of Fluids

JEE Main 2025 (Online) 28th January Morning ShiftMCQMedium📈 Topic in 22% papers+4−1
Ques. 1JEE Main 2025, 28 January (Morning Shift)

Consider following statements: Choose the correct answer from the options given below:

  1. B, C, D Only
  2. C, D, E Only
  3. A, D, E Only
  4. A, B, C Only

Answer

(2) C, D, E Only

Solution

A: Molecules at the surface have extra (potential) energy compared with those in the interior, because they have fewer neighbours attracting them. This extra surface energy per unit area is the surface tension. The statement reverses this. Incorrect.

B: Viscosity of a liquid decreases as its temperature rises. Incorrect.

C: Viscosity of a gas increases with temperature (faster molecules transfer more momentum between layers). Correct.

D: Turbulence sets in when the Reynolds number Re = v d exceeds a critical value (about 2000 for flow in a pipe). Correct.

E: The tangent to a streamline gives the velocity at that point; if two streamlines crossed, the fluid would have two velocities at one point, which is impossible. Correct.

C, D and E only are correct.

Answer: (2)

Keep practising — Mechanical Properties of Fluids

Ques. 2JEE Main 2025, 28 January (Evening Shift)

A 400 g solid cube having an edge of length 10 cm floats in water. How much volume of the cube is outside the water? (Given: density of water = 1000 kg m-3)

  1. 400 cm3
  2. 600 cm3
  3. 1400 cm3
  4. 4000 cm3
Ques. 3JEE Main 2025, 24 January (Morning Shift)

An air bubble of radius 0.1 cm lies at a depth of 20 cm below the free surface of a liquid of density 1000 kg/m3. If the pressure inside the bubble is 2100 N/m2 greater than the atmospheric pressure, then the surface tension of the liquid in SI unit is (use g=10 m/s2)

  1. 0.02
  2. 0.05
  3. 0.25
  4. 0.1
Ques. 4JEE Main 2025, 24 January (Morning Shift)

The amount of work done to break a big water drop of radius 'R' into 27 small drops of equal radius is 10 J. The work done required to break the same big drop into 64 small drops of equal radius will be

  1. 20 J
  2. 10 J
  3. 5 J
  4. 15 J
Ques. 5JEE Main 2025, 23 January (Morning Shift)

Given below are two statements: In the light of the above statements, choose the correct answer from the options given below

  1. Both Statement I and Statement II are false
  2. Both Statement I and Statement II are true
  3. Statement I is false but Statement II is true
  4. Statement I is true but Statement II is false
Ques. 6JEE Main 2025, 23 January (Evening Shift)

Water flows in a horizontal pipe whose one end is closed with a valve. The reading of the pressure gauge attached to the pipe is P1. The reading of the pressure gauge falls to P2 when the valve is opened. The speed of water flowing in the pipe is proportional to

  1. (P1-P2)2
  2. P1-P2
  3. P1-P2
  4. (P1-P2)4
Ques. 7JEE Main 2025, 23 January (Evening Shift)

An air bubble of radius 1.0 mm is observed at a depth 20 cm below the free surface of a liquid having surface tension 0.095 J/m2 and density 103 kg/m3. The difference between pressure inside the bubble and atmospheric pressure is N/m2. (Take g=10 m/s2)

Ques. 8JEE Main 2025, 22 January (Morning Shift)

Two soap bubbles of radius 2 cm and 4 cm , respectively, are in contact with each other. The radius of curvature of the common surface, in cm , is .

Ques. 9JEE Main 2025, 22 January (Evening Shift)

A tube of length L is shown in the figure. The radius of cross section at the point (1) is 2 cm and at the point (2) is 1 cm , respectively. If the velocity of water entering at point (1) is 2 m/s, then velocity of water leaving the point (2) will be [figure]

  1. 4 m/s
  2. 6 m/s
  3. 2 m/s
  4. 8 m/s
Ques. 10JEE Main 2025, 22 January (Evening Shift)

A small rigid spherical ball of mass M is dropped in a long vertical tube containing glycerine. The velocity of the ball becomes constant after some time. If the density of glycerine is half of the density of the ball, then the viscous force acting on the ball will be (consider g as acceleration due to gravity)

  1. 2Mg
  2. 32Mg
  3. Mg2
  4. Mg
Ques. 11JEE Main 2024, 9 April (Morning Shift)

A sphere of relative density and diameter D has concentric cavity of diameter d. The ratio of Dd, if it just floats on water in a tank is :

  1. ( - 2 + 2 )1/3
  2. ( + 1 - 1 )1/3
  3. ( - 1 )1/3
  4. ( - 1 )1/3

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