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Question (1)

QN0035675

A tall cylinder is filled with viscous oil. A round pebble is dropped from the top with zero initial velocity. From the plot shown in figure, indicate the one that represents the velocity of the pebble as a function of time .

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

Correct Answer: C

Explanation:

When the pebble is dropped from the top of cylinder filled with viscous oil and pebble falls under gravity with constant acceleration, but as it is dropped it enter in oil. So dragging or viscous force is

where is radius of the pebble, is instantaneous speed, is coefficient of viscosity.

As the force is variable, hence acceleration is also variable so graph will not be straight line due to viscosity of oil. First velocity increases and then becomes constant known as terminal velocity.

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Question (2)

QN0035676

Which of the following diagrams does not represent a streamline flow?

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

Correct Answer: D

Explanation:

In a streamline flow the velocity of fluid particles remaines constant across any cross-sectional area, then a point on the area cannot have different velocities at the same time, hence two streamlines flow layers do not cross each other.

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Question (3)

QN0035677

Along a streamline,

(A)
the velocity of a fluid particle remains constant
(B)
the velocity of all fluid particles crossing a given position is constant
(C)
the velocity of all fluid particles at a given instant is constant
(D)
the speed of a fluid particle remains constant

Correct Answer: B

Explanation:

In a streamline flow the velocity of fluid particles remaines constant across any cross-sectional area, then a point on the area cannot have different velocities at the same time, hence two streamlines flow layers do not cross each other.

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Question (4)

QN0035678

An ideal fluid flows through a pipe of circular cross-section made of two sections with diameters and . The ratio of the velocities in the two pipes is

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

Correct Answer: A

Explanation:

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Question (5)

QN0035679

The angle of contact at the interface of water-glass is , ethyl alcohol-glass is , mercury-glass is and methyliodide-glass is . A glass capillary is put in a trough containing one of these four liquids. It is observed that the meniscus is convex. The liquid in the trough is

(A)
water
(B)
ethylalcohol
(C)
mercury
(D)
methyliodide

Correct Answer: C

Explanation:

We observed that meniscus of liquid is convex shape as shown in figure which is possible if only, the angle of contact is obtuse. Hence, the combination will be of case of mercury-glass . Hence verifies the option (c).

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Question (1)

A tall cylinder is filled with viscous oil. A round pebble is dropped from the top with zero initial velocity. From the plot shown in figure, indicate the one that represents the velocity of the pebble as a function of time .

Explanation:

Link:

Question (2)

Which of the following diagrams does not represent a streamline flow?

Explanation:

Link:

Question (3)

Along a streamline,

Explanation:

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Question (4)

An ideal fluid flows through a pipe of circular cross-section made of two sections with diameters and . The ratio of the velocities in the two pipes is

Explanation:

Link:

Question (5)

The angle of contact at the interface of water-glass is , ethyl alcohol-glass is , mercury-glass is and methyliodide-glass is . A glass capillary is put in a trough containing one of these four liquids. It is observed that the meniscus is convex. The liquid in the trough is

Explanation:

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