Fluid Mechanics · Physics · COMEDK

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MCQ (Single Correct Answer)

1
In to a vessel containing pure water a clean glass tube of radius $3.6 \times 10^{-4} \mathrm{~m}$ is held vertically with 12 cm of the tube above the water level. Now the capillary tube is moved down in to the water so that only 2 cm of its length is above the water surface. Angle of contact $\Theta$ at this position is (given surface tension of water $=7.2 \times 10^{-2} \mathrm{Nm}^{-1}$ and $g=10 \mathrm{~ms}^{-2}$ )
COMEDK 2025 Evening Shift
2
Water from a tap emerges vertically downwards with an initial speed of $1.0 \mathrm{~ms}^{-1}$. The cross-sectional area of the tap is $1 \mathrm{~cm}^2$. Assume that the pressure is constant throughout the stream of water and that the flow is steady. The cross-sectional area of the stream 15 cm below the tap is $\left(\mathrm{g}=10 \mathrm{~ms}^{-2}\right)$
COMEDK 2025 Afternoon Shift
3
A wind mill converts a fixed fraction of the wind energy intercepted by its blades into electrical energy. The electrical power output P is related to the velocity of wind v as
COMEDK 2025 Afternoon Shift
4
A cylindrical tank 0.5 m in radius, rests on a platform 1.5 m high. Initially the tank is filled with water to a height of 2.5 m . A small plug whose area is $10^{-4} \mathrm{~m}^2$ is removed from an orifice located on the side of the tank at the bottom. The speed with which the water strikes the ground is: [Assume $g=10 \mathrm{~ms}^{-2}$ ]
COMEDK 2025 Morning Shift
5

What is the relation obeyed by the angles of contact $$\theta_1, \theta_2$$ and $$\theta_3$$ of 3 liquids of different densities $$P_1, P_2$$ and $$P_3$$ respectively $$(\mathrm{P}_1 < \mathrm{P}_2 < \mathrm{P}_3$$) when they rise to the same capillary height in 3 identical capillaries and having nearly same surface tension $$\mathrm{T}$$ ?

COMEDK 2024 Evening Shift
6

Water flows from a tap with steady flow, through a cross sectional area of $$10^{-3} \mathrm{~m}^2$$ with a speed of $$0.5 \mathrm{~ms}^{-1}$$. Assume the pressure is constant throughout the stream of water. The cross sectional area of the stream $$0.19 \mathrm{~m}$$ below the tap is

COMEDK 2024 Afternoon Shift
7

Modulus of rigidity of an incompressible liquid is

COMEDK 2024 Afternoon Shift
8

64 rain drops of the same radius are falling through air with a steady velocity of $$0.5 \mathrm{~cm} \mathrm{~s}^{-1}$$. If the drops coalesce, the terminal velocity would be

COMEDK 2024 Morning Shift
9

A block of wood floats in water with $$(4 / 5)$$ th of its volume submerged. If the same block just floats in a liquid, the density of the liquid is (in $$\mathrm{kgm}^{-3}$$)

COMEDK 2023 Morning Shift
10

A balloon with mass $m$ is descending down with an acceleration $$a$$ (where, $$a < g$$ ). How much mass should be removed from it so that it starts moving up with an acceleration $$a$$ ?

COMEDK 2023 Morning Shift
11

The speeds of air-flow on the upper and lower surfaces of a wing of an aeroplane are $$v_1$$ and $$v_2$$, respectively. If $$A$$ is the cross-sectional area of the wing and $$\rho$$ is the density of air, then the upward lift is

COMEDK 2023 Morning Shift
12

Water from a tap of cross-sectional area $$1 \mathrm{~cm}^2$$, falls vertically downwards at $$2 \mathrm{~m} / \mathrm{s}$$. The cross sectional area of the stream, $$20 \mathrm{~cm}$$ below the tap is (assume that pressure is constant throughout and the flow is streamlined; $$\left(\mathrm{g}=10 \mathrm{~ms}^{-2}\right)$$

COMEDK 2023 Evening Shift
13

A raft of density 600 g/m$$^3$$ and mass 120 kg floats in water. How much weight can be put on the raft to make it just sink?

COMEDK 2022
14

Water is poured in a tank through a cylindrical tube of area of cross-section A and ejecting water at a constant speed 4 m/s. the tank contains a hole of area $$\frac{A}{2}$$ at bottom. Level of water in the tank will not go up beyond

COMEDK 2022
15

According to Pascal's law, pressure in a fluid at rest is the same at all points, if

COMEDK 2021
16

The surface tension of a liquid at its boiling point

COMEDK 2021
17

A ball floats on the surface of water in a container exposed to the atmosphere. When the container is covered and the air is partially removed, then the ball

COMEDK 2020
18

A frame made of metallic wire enclosing a surface area A is covered with a soap film. If the area of the frame of metallic wire is reduced by 50%, then the energy of the soap film will be changed by

COMEDK 2020
19

A fluid is in streamline flow across a horizontal pipe of variable area of cross-section. For this which of the following statements is correct?

COMEDK 2020
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