Chapter 5

Question 1

A fluid flows steadily through a pipe with a uniform cross-sectional area. The density of the fluid decreases to half its initial value as it flows through the pipe. The correct statement about the average velocity V is

Answer 1

Answer: a

The velocity of a fluid in a steady flow is inversely proportional to the fluid density. Therefore, as the density decreases to half its initial value, the velocity doubles.

Question 2

Water flows steadily into and out of the system with four pipes shown below. The mass flowrate through three of the pipes in kg/s is indicated (see image).

Answer 2

Answer: d

According to the principle of conservation of mass, the mass of water flowing into the system is equal to that flowing out of the system. Therefore, (see image)

Question 3

The nozzle on a fire hose is connected to the hose via a coupling. When the fire hose is in use with water flowing through it and the hose is stationary, the coupling is:

a) in equilibrium, so there is no force on the coupling.
b) in tension.
c) in compression.

Answer 3

Answer: b

Since the reaction force developed due to the flow through the pipe is in opposite direction, there will be a tensile force developed in the coupling.

Question 4

Answer 4

Answer: c