12.3 Moving In Fluids

Question 1

What is laminar flow?

Answer 1

a flow pattern where adjacent layers of fluid do not cross into each other

Question 2

What is a turbulent flow?

Answer 2

a flow pattern where layers of fluid cross into each other, resulting in the formation of eddy currents

Question 3

In an airplane what happens when turbulent flow happens on the wings?

Answer 3

turbulence

Question 4

Why should laminar flow be used in e.g. food fillings be placed into food?

Answer 4

As otherwise air bubbles will show up?

Question 5

When does laminar flow occur?

Answer 5

When travelling slowly either the fluid or object.

Question 6

When does turbulent flow occur?

Answer 6

When travelling quickly either the fluid or object.

Question 7

What else can cause turbulent flow?

Answer 7

If the radius of tube is quite small, density and viscosity

Question 8

Explain density in this?

Answer 8

More density means more resistance to flow of motion and so smaller changes in will more are more likely to cause turbulent flow.

Question 9

What is special about laminar flow?

Answer 9

Velocity stays constant at any point of fluid.

Question 10

What is viscosity?

give example for low and high

Answer 10

Relates to fluids resistance to flow.
high = oil
low = water/ any gas

Question 11

How does viscosity affect flow?

Answer 11

The lower the viscosity the easier it is for layers of fluid to slide over each other making it less likely to cause turbulent flow.

Question 12

How can we compare viscosities? activity

Answer 12

Observing the rate of flow of substance through a funnel and a glass tube

Question 13

What is the effect of viscosity called?

Answer 13

The viscous drag

Question 14

What is viscous drag?

Answer 14

The resistance to motion due to contact between an object and a substance

Question 15

What do we use to calculate force due to viscous drag?

Answer 15

Stokes Law

Question 16

What happens to viscosity as temperature increases? Liquids

Answer 16

decrease

Question 17

What happens to viscosity as temperature decreases in gases?

Answer 17

It will increase

Question 18

Equation Stokes Law?

Answer 18

f = 6(pi)nrv 
f = force (viscous drag)
n = viscosity of fluid
r = radius of object  
v= speed of object

Question 19

What does Stokes Law only apply to?

Answer 19

Small objects moving with laminar flow

Question 20

Why does viscosity decrease with increasing temperature for liquids?

Answer 20

As molecules get more energy overcoming forces holding molecules together. This means liquid becomes more fluid.

Question 21

Why does viscosity increase with greater temperature for gases?

Answer 21

Increases Ek meaning that the frequency of collisions of air particles is greater causing more resistance to flow. Each collision transfers more Ek and therefore even more collisions happen.

Question 22

What forces act on a free falling sphere through a liquid.

Answer 22

W = weight 
U = upthrust 
F = viscous drag

Question 23

What would be the equation (w u f) on a sphere falling downwards?

Answer 23

Fr = W - (U+F)

Question 24

What would be the equation (w u f) on a sphere falling upwards?

Answer 24

Fr = U - (W+F)

Question 25

When will a sphere reach terminal velocity?

Answer 25

When W = U + F or U = W+F depending on direction of movement

Question 26

What is terminal velocity?

Answer 26

When resultant force becomes 0 and the sphere moves at constant velocity.