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Question (1)

QN0035619

As the temperature of a liquid is raised, the coefficient of viscosity

(A)
decreases
(B)
increases
(C)
remains the same
(D)
may increase or decrease depending on the nature of liquid

Correct Answer: A

Explanation:

As the temperature rises the atoms of the liquid become more mobile and the coefficient of viscosity falls.

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Question (2)

QN0035620

A boat with base area floating on the surface of a still river is intended to move with a constant speed of by the application of a horizontal force. If the river bed is deep find the force needed, (assuming a constant velocity gradient) Coefficient of viscosity of water is poise.

(A)
720 dyne
(B)
620 dyne
(C)
520 dyne
(D)
360 dyne

Correct Answer: A

Explanation:

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Question (3)

QN0035621

The relative velocity of two parallel layers of water is . If the perpendicular distance between the layers is . Then velocity gradient will be

(A)
(B)
(C)
(D)

Correct Answer: A

Explanation:

and

Velocity gradient .

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Question (4)

QN0035622

The velocity of water in a river is near the surface. If the river is deep, find the shearing stress between the horizontal layers of water. The co-efficient of viscosity of water poise.

(A)
(B)
(C)
(D)

Correct Answer: B

Explanation:

poise

Strain rate

Coefficient of viscosity,

Shearing stress strain rate

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Question (5)

QN0035623

After terminal velocity is reached, Acceleration of a body falling through a fluid is NCERT Page-264/N-192

(A)
equal to
(B)
zero
(C)
less than
(D)
greater than

Correct Answer: B

Explanation:

When terminal velocity is reached then body moves with constant velocity hence, accelesation is zero.

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Question (6)

QN0035624

According to stokes law, the relation between terminal velocity and viscosity of the medium (n) is

(A)
(B)
(C)
(D)
is independent of .

Correct Answer: C

Explanation:

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Question (7)

QN0035625

Terminal velocity of ball depends on

(A)
area of the ball
(B)
density of liquid only
(C)
density of ball only
(D)
density difference of liquid and ball

Correct Answer: D

Explanation:

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Question (8)

QN0035626

A spherical solid ball of volume is made of a material of density . It is falling through a liquid of density . Assume that the liquid applies a viscous force on the ball that is proportional to the square of its speed , i.e., . The terminal speed of the ball is

(A)
(B)
(C)
(D)

Correct Answer: A

Explanation:

The condition for terminal speed is Weight Buoyant force + Viscous force

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Question (9)

QN0035627

When a ball is released from rest in a very long column of viscous liquid, its downward acceleration is ' ' (just after release). Its acceleration when it has acquired two third of the maximum velocity is . Find the value of .

(A)
2
(B)
3
(C)
4
(D)
5

Correct Answer: B

Explanation:

When the ball is just released, the net force on ball is (= mg - buoyant force)

The terminal velocity of the ball is attained when net force on the ball is zero.

Viscous force

When the ball acquires of its maximum velocity the viscous force is

Hence net force is

required acceleration is

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Question (10)

QN0035628

A ball of radius and density falls freely under gravity through a distance before entering water. Velocity of ball does not change even on entering water. If viscosity of water is the value of is given by

(A)
(B)
(C)
(D)

Correct Answer: C

Explanation:

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Question (1)

As the temperature of a liquid is raised, the coefficient of viscosity

Explanation:

Link:

Question (2)

A boat with base area floating on the surface of a still river is intended to move with a constant speed of by the application of a horizontal force. If the river bed is deep find the force needed, (assuming a constant velocity gradient) Coefficient of viscosity of water is poise.

Explanation:

Link:

Question (3)

The relative velocity of two parallel layers of water is . If the perpendicular distance between the layers is . Then velocity gradient will be

Explanation:

Link:

Question (4)

The velocity of water in a river is near the surface. If the river is deep, find the shearing stress between the horizontal layers of water. The co-efficient of viscosity of water poise.

Explanation:

Link:

Question (5)

After terminal velocity is reached, Acceleration of a body falling through a fluid is NCERT Page-264/N-192

Explanation:

Link:

Question (6)

According to stokes law, the relation between terminal velocity and viscosity of the medium (n) is

Explanation:

Link:

Question (7)

Terminal velocity of ball depends on

Explanation:

Link:

Question (8)

A spherical solid ball of volume is made of a material of density . It is falling through a liquid of density . Assume that the liquid applies a viscous force on the ball that is proportional to the square of its speed , i.e., . The terminal speed of the ball is

Explanation:

Link:

Question (9)

When a ball is released from rest in a very long column of viscous liquid, its downward acceleration is ' ' (just after release). Its acceleration when it has acquired two third of the maximum velocity is . Find the value of .

Explanation:

Link:

Question (10)

A ball of radius and density falls freely under gravity through a distance before entering water. Velocity of ball does not change even on entering water. If viscosity of water is the value of is given by

Explanation:

Link:

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