KCL Section 1: Viscous drag (Materials)

Question 1

Describe laminar flow

Answer 1

Laminar flow: the streamlines do not cross over each other

Question 2

Describe turbulent flow

Answer 2

Turbulent flow: the streamlines do cross, leading to the formation of vortices and eddy currents.

Question 3

Generally, at what speed does laminar flow occur?

Answer 3

In general, laminar flow occurs at low speeds, and increasing the speed past a particular point (the critical speed) will cause the flow to become turbulent.

Question 4

What does critical flow rely on?

Answer 4

The critical speed depends on the fluid and the shape of the area in which it is flowing.

Question 5

What does Stokes Law need?

Answer 5

• Small spherical objects
• Moving slowly with laminar flow
• At a constant temperature

Question 6

What do the symbols in this equation refer to?

F = 6πηrv

Answer 6

F = viscous drag acting on a sphere (in a laminar flow of liquid)
η = coefficient of viscosity (the resistance to flow)
r = radius of the sphere
v = velocity of the sphere relative to the fluid

Question 7

What is more viscous water or air?

Which one requires more force to travel in?

Answer 7

Water is more viscous than air and so more force is needed to travel in water.

Question 8

A _____ temperature will decrease the viscosity

Answer 8

high

Question 9

The _____ temperature would decrease the viscosity of the water so less ______ would be needed to move. ______ is also lower

Answer 9

high
force
drag