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JEE • PHYSICS • MECHANICAL PROPERTIES OF FLUIDS

Mechanical properties of fluids practice · Medium

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Showing 31-60 of 390 questions

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31 Medium
31 of 390
Remembering +4 | -1
The lift of an air plane is based on
View answer and explanation
Correct option: B
Bernoulli's theorem
Option B (Bernoulli's theorem) is correct because the lift of an airplane wing is a direct application of Bernoulli's principle, where faster airflow over the wing creates lower pressure.
32 Medium
32 of 390
Application +4 | -1
Two copper vessels AA and BB have the same
base area but of different shapes. AA take twice
the volume of water as that BB requires to fill
upto a particular common height. Then the
correct statement among the following is:
View answer and explanation
Correct option: B
Pressure on the base area of vessels AA
and BB is same
Option B (Pressure on the base area of vessels A and B is same) is correct because the pressure at the bottom of a liquid column depends only on the height and density of the liquid, which are the same for both vessels.
33 Medium
33 of 390
Application +4 | -1
A vessel, whose boom has round holes with a diameter of 0.1mm, is filled with water. The maximum height to which the water can be filled without leakage is (S.T. of water =75dyne/cm,g=1000cm/s275\mathrm{ }dyne/cm,\mathrm{ }g\mathrm{ } = 1000\mathrm{ }cm/{s^2})
View answer and explanation
Correct option: D
30 cm
Option D (30 cm) is correct because it is calculated using the formula relating surface tension, radius, density, and gravity to the height of the water column.
34 Medium
34 of 390
Understanding +4 | -1
Assertion(A): The water rises higher in a capillary tube of small diameter than in the capillary tube of large diameter.

Reason(R): Height through which liquid rise in capillary tube inversely proportional to the diameter of capillary tube.
View answer and explanation
Correct option: A
If both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
Option A is correct because the height of liquid rise in a capillary tube is inversely proportional to the diameter of the tube, explaining why the water rises higher in a smaller diameter tube.
35 Medium
35 of 390
Application +4 | -1
A manometer connected to a close tap reads 3.5×105Nm−23.5 \times {10^5}\mathrm{N}{\mathrm{m}^{ - 2}}. When the valve is opened, the reading of manometer falls to 3.0×105Nm−23.0 \times {10^5}\mathrm{N}{\mathrm{m}^{ - 2}} , then velocity of flow of water is
View answer and explanation
Correct option: B
10ms−110\mathrm{m}{\mathrm{s}^{ - 1}}
Option B (10ms−110\mathrm{m}{\mathrm{s}^{ - 1}}) is correct because it is calculated using Bernoulli's theorem, relating the pressure difference to the velocity of the water flow.
36 Medium
36 of 390
Analyzing +4 | -1
A: Needle placed carefully on the surface of water may float, where as a ball of same material sinks
R: Archimedes principle is applicable for only spherical bodies
View answer and explanation
Correct option: A
Both A and R are true and R is the correct explanation of A
Option C is correct because a needle floats due to surface tension, while a ball sinks due to Archimedes' principle, and the reason incorrectly states Archimedes' principle only applies to spherical bodies.
37 Medium
37 of 390
Understanding +4 | -1
A: According to Archimede's principle when body is floating the weight of liquid displaced by body is equal to the weight of the body
R: A man is sitting in a boat which is floating on a pond. If the man drinks some water from the pond, the level of the water in the pond decreases
View answer and explanation
Correct option: A
Both A and R are true and R is the correct explanation of A
Option A is correct because Archimedes' principle states that the buoyant force on a floating object equals the weight of the liquid displaced, and the man drinking water causes the water level to decrease.
38 Medium
38 of 390
Remembering +4 | -1
Pressure applied to an enclosed fluid is transmitted undiminished to every point of the fluid and the walls of containing vessel. This law was first formulated by:
View answer and explanation
Correct option: C
Pascal
Option C (Pascal) is correct because Pascal's principle states that pressure applied to an enclosed fluid is transmitted undiminished to every point within the fluid.
39 Medium
39 of 390
Analyzing +4 | -1
A soap bubble of radius RR, surface tension TT exists in equilibrium in vacuum. A monoatomic gas is trapped inside the soap bubble. Charge Q\mathrm{Q} is given to bubble such that bubble expands from radius a to radius 2a2 \mathrm{a} under reversible adiabatic condition. If surface charge density on the bubble surface is found to be xε0Tya\sqrt{\frac{x \varepsilon_0 T}{y a}}. Find the value of x/y.(x,yx / y .(x, y are positive co-primes)
View answer and explanation
Correct option: A
4
The correct answer is A (4). The surface charge density is calculated using the adiabatic process and the change in radius, resulting in σ=15ε0T4a\sigma = \sqrt{\frac{{15 \varepsilon_0 T}}{{4 a}}}, thus x/y = 15/4, but the answer asks for x/y where σ=xε0Tya\sigma = \sqrt{\frac{{x \varepsilon_0 T}}{{y a}}}, and x and y are coprime. The question asks for x/y, where x and y are coprime after simplification.
40 Medium
40 of 390
Application +4 | -1
A piece of gold (ρ=19.3 g/cm3)\left(\rho=19.3 \mathrm{~g} / \mathrm{cm}^3\right) has a cavity in it. It weights 38.2 g38.2 \mathrm{~g} in air and 36.2 g36.2 \mathrm{~g} in water. The volume of the cavity in gold is
View answer and explanation
Correct option: C
0.02 cm30.02 \mathrm{~cm}^3
Option C (0.02 cm30.02 \mathrm{~cm}^3) is correct because it is the difference between the volume of water displaced and the volume of gold calculated from its mass and density.
41 Medium
41 of 390
Remembering +4 | -1
When a pinch of salt or any other salt which is soluble in water is added to water, its surface tension
View answer and explanation
Correct option: A
Increases
Option A (Increases) is correct because adding soluble salts to water generally increases its surface tension.
42 Medium
42 of 390
Application +4 | -1
A small spherical ball of steel falls through a viscous medium with terminal velocity vv. If a ball of twice the radius of the first one but of the same mass is dropped through the same method, it will fall with a terminal velocity (neglect buoyancy)
View answer and explanation
Correct option: A
v2\frac{v}{2}
Option A (v/2) is correct because the terminal velocity depends on the radius and density of the ball.
43 Medium
43 of 390
Understanding +4 | -1
Statement A: Water flows faster than honey.
Statement B: The coefficient of viscosity of water is less than honey.
View answer and explanation
Correct option: A
Statement A is true and statement B is true
Option A is correct because water indeed flows faster than honey due to its lower viscosity, and the statement about the coefficient of viscosity is also true.
44 Medium
44 of 390
Understanding +4 | -1
With the increase in temperature, the angle of contact
View answer and explanation
Correct option: A
Decreases
Option A is correct because as temperature increases, the surface tension of the liquid decreases, which generally leads to a decrease in the angle of contact.
45 Medium
45 of 390
Application +4 | -1
The velocity of kerosene oil in a horizontal
pipe is 5 ms−1.5 \, \text{ms}^{-1}. If g=10 ms−2,g=10 \, \text{ms}^{-2}, then the velocity
head of oil will be
View answer and explanation
Correct option: A
1.25 m
Option A (1.25 m) is correct because the velocity head is calculated using the formula v2/(2g)v^2 / (2g), where v is the velocity and g is the acceleration due to gravity.
46 Medium
46 of 390
Application +4 | -1
Density of ice is ρ\rho and that of water is σ\sigma. What will be the decrease in volume when a mass MM of ice melts
View answer and explanation
Correct option: C
M[1ρ−1σ]M\left[ {\frac{1}{\rho } - \frac{1}{\sigma }} \right]
Option C (M[1ρ−1σ]M\left[ {\frac{1}{\rho } - \frac{1}{\sigma }} \right]) is correct because it calculates the difference in volume between the ice and water phases using their respective densities and the given mass.
47 Medium
47 of 390
Application +4 | -1
A fluid flows through a horizontal pipe having two different cross-sections of area AA and2A2A. If the pressure at the thin cross-section is ppand fluid velocity is vv, the velocity and pressure at the thicker cross-section is (take the density of fluid as ρ\rho)
View answer and explanation
Correct option: C
v2,p+38ρv2\frac{v}{2},p + \frac{3}{8}\rho {v^2}
Option C (v/2, p + (3/8)ρv²) is correct because it applies both the continuity equation and Bernoulli's principle correctly.
48 Medium
48 of 390
Application +4 | -1
A raindrop with radius 1.5mm1.5mm falls from a cloud at a height 1200m1200\mathrm{m} from ground. The density of water is 1000kg/m31000kg/{m^3}and density of air is 1.2kg/m31.2kg/{m^3}. Assume the drop was spherical throughout the fall and there is no air drag. The impact speed of the drop will be
View answer and explanation
Correct option: B
550km/h550km/h
Option B (550km/h550km/h) is correct because it calculates the impact speed of the raindrop assuming no air drag, using the formula derived from conservation of energy.
49 Medium
49 of 390
Application +4 | -1
Work done in forming a soap bubble of radius R{R} is W{W} then work done in forming a soap bubble of radius 2R2 {R} will be:
View answer and explanation
Correct option: B
4W4 {W}
Option B (4W4 {W}) is correct because the work done is proportional to the surface area of the soap bubble, which is proportional to the square of the radius.
50 Medium
50 of 390
Understanding +4 | -1
A: Machine parts are jammed in winter.
R: The viscosity of lubricant used in machine parts increase at low temperature.
View answer and explanation
Correct option: A
Both A and R are true and R is the correct explanation of A
Option A (Both A and R are true and R is the correct explanation of A) is correct because the viscosity of lubricants increases at low temperatures, causing machine parts to jam.
51 Medium
51 of 390
Application +4 | -1
In Millikan's oil drop experiment, what is the terminal speed of a drop of radius 2.0×10−5 m2.0 \times 10^{-5} \mathrm{~m} and density 1.2×103 kg m−31.2 \times 10^3 \mathrm{~kg} \mathrm{~m}^{-3}? Take the viscosity of air at the temperature of the experiment to be 1.8×10−5 Nsm−21.8 \times 10^{-5} \mathrm{~Nsm}^{-2}. How much is the viscous force on the drop at that speed? Neglect buoyancy of the drop due to air.
View answer and explanation
Correct option: A
3.9×10−10 N3.9 \times 10^{-10} \mathrm{~N}
Option A (3.9×10−10 N3.9 \times 10^{-10} \text{ N}) is correct because it is calculated using Stokes' law for viscous force at terminal speed.
52 Medium
52 of 390
Application +4 | -1
A capillary tube of radius rr can support a liquid of weight 6.28×10−4 N6.28 \times 10^{-4} \mathrm{~N}. If the surface tension of the liquid is 2×10−2 N/m2 \times 10^{-2} \mathrm{~N} / \mathrm{m} then find:

(1) Radius of capillary tube.

(2) Internal circumference of capillary tube.
View answer and explanation
Correct option: C
5,31.45 , 31.4
Option C (5,31.45 , 31.4) is correct because the radius is calculated using the formula relating surface tension, radius, and weight, and the circumference is then calculated from the radius.
53 Medium
53 of 390
Analyzing +4 | -1
Two spherical bubbles are in contact with each other internally as shown. The radius of curvature of the common surface is R, then -
View answer and explanation
Correct option: C
R<R2\mathrm{R} < \mathrm{R}_2
Option C (R<R2\mathrm{R} < \mathrm{R}_2) is correct because the pressure difference is largest between the atmosphere and the smaller bubble, leading to the smallest radius of curvature for the common surface.
54 Medium
54 of 390
Application +4 | -1
Two capillary of length L and 2L and of radii R and 2R are connected in series. The net rate of flow of fluid through them will be (given rate of the flow through single capillary, X= πpR48ηL\frac{{\pi p{R^4}}}{{8\eta L}})
View answer and explanation
Correct option: A
89X\frac{8}{9}X
Option A (89X\frac{8}{9}X) is correct because when two capillaries are connected in series, the net rate of flow is inversely proportional to the equivalent fluid resistance, which changes by a factor of 9/8.
55 Medium
55 of 390
Application +4 | -1
The level of water in a tank is 5 m5 \mathrm{~m} high. A hole of area 1 cm21 \mathrm{~cm}^2 is made at the bottom of the tank. The rate of leakage of water from the hole is (Take, g=10 ms−2g=10 \mathrm{~ms}^{-2} )
View answer and explanation
Correct option: A
10−3 m3 s−110^{-3} \mathrm{~m}^3 \mathrm{~s}^{-1}
Option A (10−3 m3 s−110^{-3} \mathrm{~m}^3 \mathrm{~s}^{-1}) is correct because it's calculated using the formula for the rate of leakage, which is A2ghA \sqrt{2gh}.
56 Medium
56 of 390
Remembering +4 | -1
Spherical ball of radius RR are falling in a viscous fluid of viscosity ɳ with a velocity vv. The retarding viscous force acting on the spherical ball is
View answer and explanation
Correct option: B
directly proportional to both radius RR and velocity vv
Option B (directly proportional to both radius R and velocity v) is correct because the viscous force is given by Stokes' law: F = 6πηRv.
57 Medium
57 of 390
Understanding +4 | -1
A: The blood pressure in human is greater at the feet than at the brain
R: Pressure of liquid at any point is proportional to height, density of liquid and acceleration due to gravity
View answer and explanation
Correct option: C
A is true but R is false
Option C (A is true but R is false) is correct because blood pressure is indeed greater at the feet than at the brain due to hydrostatic pressure, but the provided reason is incomplete as it doesn't account for the effect of the heart's pumping action.
58 Medium
58 of 390
Analyzing +4 | -1
This question has statement -I and statement-II of the four choices given after the statements. Choose the one that best describes the two statements.
Statement-I: A capillary tube is dipped in a liquid rises to a height hh in it. As the temperature of the liquid is raised, the height hh decreases (if the density of the liquid and the angle of contact remain the same)
Statement-II: Surface tension of a liquid decreases with the rise in its temperature.
View answer and explanation
Correct option: A
Statement I and statement II are true and statement II is correct explanation of statement I
Option A is correct because the height a liquid rises in a capillary tube decreases with increasing temperature due to the decrease in surface tension, as stated in Statement II, which explains Statement I.
59 Medium
59 of 390
Analyzing +4 | -1
A piece of ice is floating in a beaker containing thick sugar solution of water. As the ice melts, the total level of the liquid
View answer and explanation
Correct option: A
Increases
Option A (Increases) is correct because the volume of water produced by the melting ice is greater than the volume of the sugar solution displaced by the ice.
60 Medium
60 of 390
Application +4 | -1
An iron sphere of mass 20×10−320 \times {10^{ - 3}}kg falls through a viscous liquid with terminal velocity 0.5ms−10.5\mathrm{m}{\mathrm{s}^{ - 1}}. The terminal velocity (inms−1)\left( {\mathrm{inm}{\mathrm{s}^{ - 1}}} \right) of another iron sphere of mass 54×10−254 \times {10^{ - 2}} kg is
View answer and explanation
Correct option: A
4.5
Option A (4.5) is correct because terminal velocity is proportional to the square of the radius, and thus related to mass by v∝M2/3v \propto M^{2/3}.
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