Video Transcript
Fill in the blank. Where a fluid flows steadily, the
direction of flow can change within blank of the regions of the fluid. (A) None, (B) only some, or (C)
all.
In this question, we are asked to
fill in the blank in order to make this statement true. We need to figure out the regions
in which the direction of a steady flow can change. Before we can work out what should
go in the blank, let’s remind ourselves of some information about the flow of fluids
and the difference between the types of flows.
Fluids are made up of many
particles that are not bound together. Because there are so many particles
in a fluid, it’s much easier to think about fluids in terms of their overall
flow. Recall that turbulent flow is
defined as a flow where the particles in the fluid are changing direction and/or
speed rapidly. On the other hand, steady flow is
defined as a flow where the particles in the fluid are not changing speed or
direction as often. And all have similar speeds and
directions to each other. Turbulence can be caused by
something blocking an area in the space the fluid is flowing in, like seen here. When a fluid is flowing steadily,
it is free to move in the same direction with the same speed uninterrupted, like
seen here.
Going back to the question, we are
trying to figure out whether the direction of flow can change in any region of a
steady fluid. If we look at the diagram we have
made for a fluid flowing steadily, we can see that the direction of flow is able to
change freely. Initially, the flow is
horizontal. The direction of flow then changes,
so the fluid is moving at a steeper angle. Then, the direction of flow changes
again, once more becoming horizontal.
Looking at the options we are given
to fill the blank in, we found no restrictions on where the direction of flow can
change, which means options none and only some cannot be the right answer. Those answers would mean that the
flow is restricted from changing in some or all areas. And there is no reason why this
would be the case. So, the direction of flow must be
free to change in all regions of the fluid.
So option (C), all, is the correct
answer. And our final statement reads
“Where a fluid flows steadily, the direction of flow can change within all of the
regions of the fluid.”
