Chapter 12- Fluids

Question 1

Fluid is

Answer 1

A material that flows

Liquid or gas

Question 2

Density eq

Answer 2

Mass/ volume

Symbol = rho ‘p’

Question 3

Find density of air

Answer 3

Vacuum out air of a flask
De clip and put tube into water so it draws in water to replace air lost
Then you can see the density of the air

Question 4

Pressure above you when swimming

Answer 4

Created by WEIGHT of water above you

Question 5

Air pressure in atmosphere =

Answer 5

1.0 x10^5 Pa

Question 6

Pressure in fluids eq

Answer 6

Pressure at base= weight of column/area = mg/A = Vpg/A

Volume of column (V) = Ah

Therefore

p= h’p’g

Question 7

Upthrust =

Answer 7

Weight of the displaced fluid

Question 8

Archimedes principle

Answer 8

States that when a body is totally or partially immersed in a fluid, it experiences an upthrust equal to the weight of the fluid displaced

Question 9

Flotation

Answer 9

Will float if upthrust (weight of fluid displaced) is equal to weight of object

Question 10

Example of flotation

Answer 10

A sea vessel must displace more of the less dense fresh water to balance its weight and so it lies deeper in fresh water than the salt water

Question 11

Streamlines

Answer 11

Represent velocity of a fluid at each point within it

Drawn as arrowed lines showing paths taken by small regions of the fluid

Question 12

Laminar flow

Answer 12

Occurs when adjacent layers of fluid do not cross into each other

Question 13

Turbulent flow

Answer 13

Occurs when layers of fluid cross into each other, resulting in the formation of vortices or eddy currents

Question 14

Viscosity

Answer 14

The ability of a fluid to flow

As in a high viscosity means it can’t flow (e.g. Syrup)

Question 15

Which device to compare viscosity

Answer 15

Redwood viscometer

Question 16

Stokes law def

Answer 16

States that for a sphere moving through a fluid, the viscous drag acting on it is given by the eq.

Provided the movement of the fluid relative to the sphere is laminar

Question 17

How is viscous drag created on a sphere

Answer 17

Sphere moves slowly through a fluid
Movement of the fluid relative to the sphere is laminar
Molecules of the fluid adhere to the surface of the sphere and move along with it
Creating a viscous drag between the other layers of fluid

Question 18

Terminal velocity

Answer 18

Reached when a body moving trough a fluid’s resultant forces acting on it equal zero

Question 19

Terminal velocity eq

Answer 19

Fr = W - (U+F)

U+F = W

Question 20

How to measure viscosity of a liquid

Answer 20

Falling ball bearing method

Measuring cylinder full of liquid
Time taken for it to fall between each level is taken
When timings become similar is when terminal velocity has been reached

Question 21

Viscosity and temperature

Answer 21

When temp of fluid rises it’s internal energy increases. The adhesive forces between molecules and the cohesive forces at solid surfaces decrease causing a reduction in viscosity
Hot fluids become more ‘runny’

Question 22

Thixotropy

Answer 22

Viscosity reduces as the rate of flow increases

I.e. Toothpaste when pressure is applied