Tag: viscosity

Questions Related to viscosity

For an ideal fluid, viscosity is:

viscosity option b: engineering physics properties of matter physics

  1. zero

  2. infinity

  3. finite but small

  4. unity

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Correct Option: A
Explanation:

A fluid that has no resistance to shear stress between its layers is known as an ideal fluid.(Definition).Hence ideal fluid  has zero viscosity.

The total area of wings of an aeroplane is $10\, m^2$. the speed of air above and below the wings is 140 m/s and 110 m/s. Then the force on the aeroplane by air is ? $(P _A=1.28\dfrac{Kg}{m^3})$

viscosity option b: engineering physics properties of matter physics

  1. 48750 N

  2. 48000 N

  3. 95000 N

  4. 50000 N

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Correct Option: A

Viscous force a is similar to friction in solids ,but viscous force
a. is independent of area but friction depends on area
b. is temperature dependent while friction force between solids depends upon normal reaction
c. is velocity dependent while friction is velocity independent

viscosity option b: engineering physics properties of matter physics

  1. a, b, c are correct

  2. a, c are correct

  3. b, c are correct

  4. a, b are correct

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Correct Option: C
Explanation:

Viscosity depends of mass of body, temperature, velocity and density.
Where as friction depends only on normal reaction.

The viscous force on a small sphere of radius $R$ moving in a fluid varies as 

viscosity option b: engineering physics properties of matter physics

  1. $\propto \ R^2$

  2. $\propto \ R$

  3. $\propto \ (\dfrac{1}{R})$

  4. $\propto \ (\dfrac{1}{R})^2$

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Correct Option: B

Why does the cotton wick in an oil filled lamp keep on burning?

viscosity option b: engineering physics properties of matter physics

  1. By friction

  2. By capillary action

  3. By electrostatic force

  4. By Gravitational force

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Correct Option: B
Explanation:

Due to surface tension of oil capillary rise can be seen in cotton wick which makes lamp to burn.

When a ball is released from rest in a very long column of viscous liquid, its down ward acceleration is $a'$ (just after released). Its acceleration when it has acquired to third of the maximum velocity is $a/X$. Find the value of $X$.

viscosity option b: engineering physics properties of matter physics

  1. $2$

  2. $3$

  3. $23$

  4. $5$

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Correct Option: B

A liquid rises in a capillary tube when the angle of contact is:

viscosity option b: engineering physics properties of matter physics

  1. $An\ acute\ one$

  2. $An\ obtuse\ one$

  3. $\pi/2\ radian$

  4. $\pi\ radian$

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Correct Option: A
Explanation:

If angle of contact is acute, liquid rises in a capillary tube whereas if angle of contact is obtuse, liquid is depressed in a capillary tube.

Hence, option A is correct.

Two solid metal balls of radii $r$ $2r$ are falling with their terminal speeds in a viscous liquid.What is the ratio of drag force acting on these two balls?

viscosity option b: engineering physics properties of matter physics

  1. 1;2

  2. 1;4

  3. 1;8

  4. 4;1

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Correct Option: C

We have three beakers A, B and C containing glycerine, water and kerosene respectively. They are stirred vigorously and placed on the table. The liquid which comes to rest at the earliest is

viscosity option b: engineering physics properties of matter physics

  1. Glycerine

  2. Water

  3. Kerosene

  4. All of them at the same time

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Correct Option: A

When $200 ml$ of water is subjected to a pressure of $2 \times {10^8}pa,$ the decrease in its volume is $0.2 ml.$ the compressibility of water is -----

viscosity option b: engineering physics properties of matter physics

  1. $5 \times {10^{ - 8}}{m^2}{N^{ - 1}}$

  2. $5 \times {10^{ - 10}}{m^2}{N^{ - 1}}$

  3. $5 \times {10^{ - 12}}{m^2}{N^{ - 1}}$

  4. $None$

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Correct Option: C