12.2 Density + Pressure

Question 1

What are the 3 properties of fluids

Answer 1

Density,pressure and floatation

Question 2

What is density?

Answer 2

The compactness of a substance. How much space the mass takes up.

Question 3

What is the equation for density ? What do the symbols stand for?

Answer 3

p = m/v 
p = density 
m = mass 
v = volume

Question 4

What does density depend on?

Answer 4

Depends on what the object is made out of

Question 5

What can the average density be used to determine?

Answer 5

Whether the object floats or sinks.

Question 6

What is the symbol for density?

Answer 6

rho (p)

Question 7

what is a fluid

Answer 7

a material that flows

Question 8

how do the volumes of fluids change as they are heated and why

Answer 8

• their volumes increase
• this is because their particles which can slide past each other gain more kinetic energy when heated
• meaning that the amplitude of their vibrations increase so the space between them increases
• leading to an increased volume

Question 9

if the volume of a fluid with a fixed mass increases, what happens to its density

Answer 9

• its density decreases
• using the formula density = mass / volume
• a constant mass with a larger volume (denominator) leads to a lower density

Question 10

what is the main difference between how the particles in liquids and gases can be handled or manipulated

Answer 10

• liquids are more or less incompressible
• due to their particles always touching but being able to move around past each other
• however gases are compressible or can be readily squeezed
• due to their particles not always being in contact with each other

Question 11

what conditions should densities normally be measured in

Answer 11

• RTP

Question 12

How would you find the density of air practical ?

Answer 12

A flask with water is placed onto balance and mass is measured. Air should then be removed using a vacuum pump and flask reweighted so that the mass of gas removed is found. Then the beaker with the air is connected by a tube with a beaker of water. The water is forced into the other beaker by external air pressure and so the volume of water in beaker will equal volume of air.

Question 13

How many grams is one litre?

Answer 13

1000

Question 14

what is 1ml in cm?

what is 1ml in m?

Answer 14

1cm^3

1x10^-6

Question 15

1L to cm?

1L to m?

Answer 15

1000cm^3

0.001m^3

Question 16

if you dive to the bottom of a swimming pool, why do you feel the pressure pushing into your ears

Answer 16

• the pressure is created by the weight of the water above you
• so the deeper you go, the more water there is above you so more of its weight or pressure would be exerted on you

Question 17

what is the normal equation for pressure

Answer 17

• pressure = force / area

- p = F / A

Question 18

What is pressure measured in?

Answer 18

PA or Nm^-2

Question 19

normal equation for pressure?

Answer 19

p = f/a 
pressure = force / area

Question 20

What is pressure?

Answer 20

The amount of force applied over an area.

Question 21

What is the equation for pressure acting on an object in a fluid?

Answer 21

p = hpg 
pressure = height x density x gravitational field strength

Question 22

if you had a column of liquid with the density p, that had a height and a circular base, what would the initial equation for the pressure exerted on the base by that column of water be

Answer 22

pressure at the base = weight of column / area of base

Question 23

how would you manipulate that equation to include volume

Answer 23

• weight of column / area
• weight = mass x gravity (mg)
• mg / A
• as density = mass / volume, m = Vp
• replace m in the equation to get Vpg / A

Question 24

What is mass? in terms of rho

Answer 24

volume x density

Question 25

what would the final formula for the pressure at the base then be if that equation for volume is implemented

Answer 25

• as V = Ah
• Vpg / A = Ahpg / A
• simplifies to phg
• so pressure due to a column of liquid (p) = p(density)hg

Question 26

is the pressure on earth constant through out and why

Answer 26

• it is not
• gases are more compressed in the lower regions due to greater temperature and thus kinetic energy
• therefore density is lower as altitude increases