Question

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

I have been asked this question by my college director while I was bunking the class.

I want to ask this question from Types of Flow Lines topic in chapter Kinematics of Flow and Ideal Flow of Fluid Mechanics

Answer 1

Right option is (c) Pathlines of two particles in an one-dimensional flow can intersect only if the two particles move along the same direction

For 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.