Question

In a streamline (laminar flow), the velocity at any point in the liquid
(A) Does not vary with time
(B) May vary in direction but not in magnitude
(C) May vary in magnitude but not in direction

Answer 1

Hint
The movement of liquid is generally referred to as flow of liquid. Concept that describes how fluids behave and interact with their surrounding environment is known as fluid dynamics. Flow of liquid can be either steady or unsteady.

Complete step by step answer
We have seen the water flowing from a tap having a smooth texture when the flow rate is low it is known as streamline, but as the flow rate is increased, disturbances in flow is seen, it is known as turbulent flow. If we introduce a stream of ink during the smooth flow, the ink flows without mixing with the water. If we introduced the ink to the turbulent flow, we can see the mixing of ink with the water
In streamline flow the fluids flow in parallel layers such that there is no disruption of the layers and at a given point, the velocity of each fluid particle passing by remains constant with time.
As a result, the conservation equations may be applied to the flow within a given stream tube, and consequently the streamline pattern provides considerable insight into the velocity and pressure changes.
From the above discussion, we can say that the velocity at any point in the liquid is constant and does not vary with time.
Hence the correct answer is option (A) does not vary with time.

Note
Flow of liquid depends on the frame of reference. If a flow of liquid is observed by two observers in two different frames, one observer may be an unsteady flow and another observer in a different frame may observe steady flow with constant streamlines.