Chapter 6 - Fluids and Solids Flashcards

You may prefer our related Brainscape-certified flashcards:
1
Q

Define the equation for density

A

Density = mass / volume

*density of a liquid is constant, they are incompressible

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Define the equation for specific density

A

Specific density = density of substance / density of water

*density of water often 1 so specific density = density of substance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Define the equation for pressure and units for Pa and ATM

A
Pressure = force / area
Pressure = density x gravity x depth

Pascals 1 Pa = 1 N/m^2
1 atm = 1.01 x 10^5 Pa

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is buoyance and its equation

A

Fb = volume x density of fluid displaced x gravity
= mass x gravity

Buoyance is the upward force equal to the weight of fluid displaced that an object experiences in water.
An object floating must at least be displacing its own weight.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is relative density (specific gravity)?

A

relative density (or specific gravity) = height below surface of liquid

eg. if specific gravity =0.9 then 90% of that object is immersed in water.
* less dense objects float

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Define gauge pressure

A

GP = Patm +

difference in pressure of in an object compared to outside the object. Eg. gauge pressure of tyres refers to difference in pressure between tyres and in atmospheric pressure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Define absolute pressure and its equation

A

Absolute pressure is pressure of a liquid relative to pressure in a vacuum.

Asbolute pressure = atmospheric pressure + gauge pressure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Define viscosity, its equation and its relation to momentum

A

Viscosity is the resistance to flow of layers of liquid. The greater the transfer of momentum, the more energy lost
Viscosity is a measure of efficiency of momentum transfer

↑ viscosity = ↑ transfer of momentum = ↓ mechanical energy

V = (force/area) / velocity/distance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Define the two equations for pressure

A
pressure = force / area or P = work / volume
pressure = diameter x gravity x density
  • when velocity increases, pressure decreases
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Define the equation for Reynolds number and what it measures

A

R = velocity x diameter x density / viscosity coefficient
Measures if a fluid flow is streamline or turbulent
R<2000 is streamline
R>2000 is turbulent
Increase in R is increase in turbulance
decreasing temp causes increase in viscosity and a decrease in R

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Define the two equations for surface tension and its relation to potential energy

A

Potential energy = surface tension x area

Surface tension = force of contraction of surface / length along surface

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

The radius of a vessel decreases by 20%, the flow rate is the same, how much does the velocity change?

A
A1 V1 = A2 V2 = constant
If the diameter decreases, velocity (pressure) will increase
Area of a vessel is pi x radius^2
assume A + V = 1
therefore a decrease means radius2 = 0.8
0.8^2 = 0.64 area or A2
A1 V1 = A2 V2
1 x 1   = 0.64 x V2
1 x 1/0.65 = 1.5 therefore velocity will increase by 50%
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Fluid flows into a pipe with a diamter 0.5m at a rate of 5m/s. What is the rate at the other end with a diamter of 2m

A

A1V1 = A2V2

  1. 5 x 5 = 2 x ?
  2. 5 = 2 x 1.25 or 2/5
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Density of water is 0.98 and mercury is 13.6. What percentage of the height of ice would be above the surface?

A

0.98 / 13.6 = 1/14 = 7%
but to get the percentage ABOVE the water
100 - 7 = 93%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly