Deck 6: Life in a Fluid Medium

Question 1

The Reynolds number increases when

A) Water velocity decreases
B) Size of the object increases
C) Water velocity increases
D) Both b and c

Answer 1

D

Question 2

Which of the following is true?

A) Dynamic viscosity of air is greater than water
B) Dynamic viscosity increases with increasing temperature
C) Dynamic viscosity increases as the size of a particle in a fluid decreases
D) None of the above

Answer 2

D

Question 3

A bacterium likely lives

A) Under high Reynolds number conditions
B) Dominated by inertia
C) Dominated by viscosity
D) Under conditions only of very low dynamic viscosity

Answer 3

C

Question 4

Within a boundary layer

A) Flow is always turbulent
B) Water velocity is less than in the mainstream
C) Water velocity is zero
D) Reynolds number is always higher than in the mainstream

Question 5

Bernoulli's principle predicts

A) That pressure varies inversely with flow velocity
B) That velocity varies with cross-sectional area
C) That pressure near an object increases as water velocity increases
D) That small objects sink at constant velocity

Question 6

In a system of pipes, if water enters the system at a given velocity, what happens if the cross-sectional area triples?

A) Velocity triples
B) No effect on velocity
C) Velocity decreases to the third power of initial velocity
D) Velocity decreases to one-third the initial velocity

Question 7

You can reduce drag on a fixed object in a fluid by

A) Increasing the cross-sectional area exposed to the flow
B) Decreasing the cross-sectional area exposed to the flow
C) Adding projections out from the side to break up the flow
D) Changing its density

Question 8

If pressure drag is acting on an object in moving water

A) The velocity downstream of the object is greater than upstream
B) The velocity downstream of the object is always laminar
C) The velocity downstream of the object is less than upstream
D) None of the above

Question 9

Skin friction at the surface of a fish can be reduced by

A) Swimming faster
B) Swimming slower
C) Having an irregular surface with small bumps
D) None of the above

Question 10

Inertial forces dominate strongly when

A) Re < 1
B) Re < 200
C) Re > 1000
D) Re > 10