# Fluid Mechanics Questions and Answers – Types of Flow Lines

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This set of Fluid Mechanics Multiple Choice Questions & Answers (MCQs) focuses on “Types of Flow Lines”.

1. What will be the shape of the pathline for an one-dimensional flow be like?
a) straight line
b) parabolic
c) hyperbolic
d) elliptical

Explanation: A pathline is the path followed by a particle in motion. For an one-dimensional flow, the fluids move in only one dimension (say x). Hence the pathline will also be a straight line (along that direction).

2. Which of the following is correct?
a) Pathlines of two particles in an one-dimensional flow can never intersect
b) Pathlines of two particles in an one-dimensional flow can never intersect if the two particles move along the same direction
c) Pathlines of two particles in an one-dimensional flow can intersect only if the two particles move along the same direction
d) Pathlines of two particles in an one-dimensional flow can intersect only if the two particles move along different directions

Explanation: The pathline of a particle in an one-dimensional flow is a straight line along the direction it moves. If the two particles move along the same direction, their pathlines will be parallel to each other and will never intersect.

3. What is the maximum number of times the pathlines of two particles can intersect in an one dimensional flow?
a) 0
b) 1
c) 2
d) infinite

Explanation: The pathline of a particle in an one-dimensional flow is a straight line along the direction it moves. When two particles move in the same direction, their pathline will never intersect and when they move in different directions, their pathlines will intersect only once.
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4. The velocity of a point in a flow is
a) along the streamline
b) tangent to the streamline
c) along the pathline
d) tangent to the pathline

Explanation: A pathline is the path followed by a particle in motion whereas a streamline is an imaginary line within the flow such that the tangent at any point on it indicates the velocity at that point.

5. Which of the following is correct?
a) A streamline can intersect itself and two streamlines can cross
b) A streamline cannot intersect itself but two streamlines can cross
c) A streamline can intersect itself but two streamlines cannot cross
d) A streamline cannot intersect itself and two streamlines cannot cross

Explanation: A streamline is defined as an imaginary line within the flow such that the tangent at any point on it indicates the velocity at that point. At a point, there can only be one direction of velocity. Hence, neither can a streamline intersect itself nor can two streamlines cross each other.

6. If three sets of streamlines A, B and C are considered across section 1-2, which set will represent accelerated flow from 1 to 2? a) A
b) B
c) C
d) None of the sets

Explanation: Streamline spacing varies inversely as the velocity. Higher the velocity, closer will be the streamlines. Hence, converging of streamlines from 1 to 2 will indicate accelerated flow as in set A.

7. The streamlines of the particles in a flow are recorded. If the streamline distribution remain the same even after sometime, what type of flow can it be?
c) uniform
d) non-uniform

Explanation: A streamline is defined as an imaginary line within the flow such that the tangent at any point on it indicates the velocity at that point. In a steady flow, the velocity of the particles is constant with time. Hence, the streamlines remain the same even after sometime.

8. If the streamlines of the particles in a flow are parallel to each other, what type of flow can it be?
c) uniform
d) non-uniform

Explanation: Streamline spacing varies inversely as the velocity. In a uniform flow, the velocities of the particles are the same at every instant of time. Hence, the spacing between their streamlines will be the same. In other words, the streamlines will be parallel.

9. Which of the following is correct?
a) the movement of fluid mass can either be along the streamlines or across them
b) the movement of fluid mass can be along the streamlines but never across them
c) the movement of fluid mass can never be along the streamlines but can be across them
d) the movement of fluid mass can neither be along the streamlines or across them

Explanation: A streamline is defined as an imaginary line within the flow such that the tangent at any point on it indicates the velocity at that point. Flow can only be along the velocity, never perpendicular to it. Hence, the movement of fluid mass can only be along the streamlines and never across them.

10. Which of the following is correct?
a) pathlines are concerned with a number of particles at the same instant and streamlines with a particular particle at successive instants of time
b) pathlines are concerned with a particular particle at successive instants of time and streamlines with a number of particles at the same instant
c) both pathlines and streamlines are concerned with a number of particles at the same instant
d) both pathlines and streamlines are concerned with a particular particle at successive instants of time

Explanation: A pathline is the path followed by a particle in motion whereas a streamline is an imaginary line within the flow such that the tangent at any point on it indicates the velocity at that point. Thus, pathlines are concerned with a particular particle at successive instants of time and streamlines with a number of particles at the same instant.

11. The path taken by the smoke coming out of a chimney (in concentric circles) represents a
a) pathline
b) streamline
c) streakline
d) streamtube

Explanation: A pathline is the path followed by a particle in motion whereas a streamline is an imaginary line within the flow such that the tangent at any point on it indicates the velocity at that point. A streamtube is a collection of streamlines. A streakline is a curve which gives an instantaneous picture of the location of the fluid particleswhich have passed through a given point.
Hence, the path taken by the smoke coming out of a chimney (in concentric circles) will represent streaklines.

12. Which of the following is correct?
a) In steady flow, pathlines and streamlines are identical
b) In steady flow, pathlines and streaklines are identical
c) In steady flow, streaklines and streamlines are identical
d) In steady flow, pathline, streamlines and streaklines are all identical

Explanation: In case of a steady flow, the velocity at a point remains constant with time. Thus, there will be no geometrical distinction between the pathlines, streamlines and streaklines.

13. Which of the following is correct?
a) There will be no flow across the streamtube
b) There will be no flow along the streamtube
c) There will be no flow both across the streamtube and along it
d) There will be flow both across the streamtube and along it

Explanation: Streamtube is a fluid mass bounded by a group of streamlines. Since, the movement of the fluid mass can only be along the streamlines and never across them, there will be no flow across the streamtube.

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