12.2 Density + Pressure Flashcards
What are the 3 properties of fluids
Density,pressure and floatation
What is density?
The compactness of a substance. How much space the mass takes up.
What is the equation for density ? What do the symbols stand for?
p = m/v p = density m = mass v = volume
What does density depend on?
Depends on what the object is made out of
What can the average density be used to determine?
Whether the object floats or sinks.
What is the symbol for density?
rho (p)
what is a fluid
a material that flows
how do the volumes of fluids change as they are heated and why
- 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
if the volume of a fluid with a fixed mass increases, what happens to its density
- its density decreases
- using the formula density = mass / volume
- a constant mass with a larger volume (denominator) leads to a lower density
what is the main difference between how the particles in liquids and gases can be handled or manipulated
- 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
what conditions should densities normally be measured in
- RTP
How would you find the density of air practical ?
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.
How many grams is one litre?
1000
what is 1ml in cm?
what is 1ml in m?
1cm^3
1x10^-6
1L to cm?
1L to m?
1000cm^3
0.001m^3
if you dive to the bottom of a swimming pool, why do you feel the pressure pushing into your ears
- 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
what is the normal equation for pressure
- pressure = force / area
- p = F / A
What is pressure measured in?
PA or Nm^-2
normal equation for pressure?
p = f/a pressure = force / area
What is pressure?
The amount of force applied over an area.
What is the equation for pressure acting on an object in a fluid?
p = hpg pressure = height x density x gravitational field strength
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
pressure at the base = weight of column / area of base
how would you manipulate that equation to include volume
- 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
What is mass? in terms of rho
volume x density
what would the final formula for the pressure at the base then be if that equation for volume is implemented
- as V = Ah
- Vpg / A = Ahpg / A
- simplifies to phg
- so pressure due to a column of liquid (p) = p(density)hg
is the pressure on earth constant through out and why
- 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
