Topic 2 - Pressure and density Flashcards
Equations
Density = mass ÷ volume
e = m ÷ V
Pressure = force ÷ area
p = F ÷ A
Pressure difference = height x density x gravitational field strength
p = h x e x g
Pressure in a gas or a liquid at rest acts what?
Pressure in a gas or a liquid at rest acts equally in all different direction (Pascals law)
Density and the unit
Describes how closely packed the particles are in a solid, liquid or gas. Density is the amount of mass per unit volume, or kilograms per cubic metre, symbol kg/m3. It is sometimes grams per cubic centimetre (g/cm3).
Mass is defined as-
The amount of matter that an object contains
Volume is defined as and the unit
The amount of space an object takes up. The unit of mass is m^3
The amount of space an object takes up and the unit
The unit of volume is the Cubic metre, m3.
STEP 1: DENSITY OF A REGULAR SOLID
As regular solids you can take cubes or cuboids (with sides of different lengths) of various materials.
Equipment list:
1.Cubes/cuboids of different materials
2.Ruler
3.Mass balance
Procedure:
1.Measure the mass of the cube/cuboid using a mass balance.
2.Measure each side of the cube/cuboid with a ruler
3.Calculate the volume of the cube/cuboid using the measurements of its sides
4.Calculate the density of the cube/cuboid by dividing the mass by the volume.
STEP 2: DENSITY OF AN IRREGULAR SOLID
MAIN IDEA:
THE OBJECT IN WATER WILL DISPLACE A VOLUME OF WATER EQUAL TO ITS OWN VOLUME
Depending on the size of the irregular shaped solid, you will either carry out the experiment only using a top pan balance and a measuring cylinder (for small objects as in the first picture) or using a top pan balance and the combination of a Eureka can and a measuring cylinder (for bigger objects as in the second picture).
Equipment list:
1.Irregular shaped objects of different materials
2.Top pan balance
3.Measuring cylinders
4.Eureka can (displacement can)
Procedure (if the object fits in a measuring cylinder):
1.Measure and record the mass of the object
2.Pour some water into the measuring cylinder, measure and record its volume
3.Put the object in the measuring cylinder, measure and record the new volume
4.Using the main idea underlined above, calculate and record the volume of the object
5.Calculate and record the density of the object
Procedure (if the object does not fit in a measuring cylinder):
1.Measure and record the mass of the object
2.Fill a Eureka can with water up to the nozzle and place a measuring cylinder under the nozzle
3.Put the object in the Eureka can and measure the volume of water displaced in the cylinder
4.Record the volume of the object
5.Calculate the density of the object
STEP 3: DENSITY OF A LIQUID
Equipment list:
1.Liquids of different densities
2.Measuring cylinder
3.Mass balance
Procedure:
1.Measure the mass of the empty measuring cylinder and note it down in a table
2.Now pour an easy to read volume of liquid into the measuring cylinder
3.Measure the mass of the measuring cylinder with the liquid inside (and note it down)
4.Calculate the mass of the liquid alone. Note it down in your table
5.Measure and note down the volume of liquid
6.Calculate the density of the liquid
Pressure is defined as and the unit
Pressure is defined as the Force per unit Area (concentration of force).
The unit for pressure is the Pascal (Pa).
Force - unit
Force is measured in Newtons, N
Area - unit
Area is measured in square metres, m2.
Pressure in a fluid at rest…
Pressure in a fluid at rest acts equally in all direction. This can be demonstrated by piercing a bag of water all the way around at the same height and observing the jets of water reaching equal distances. We have, however, all experienced how pressure in a fluid increases with depth.
Force by an object under water..
The force felt by an object under water is equal to the weight of all the water above it.
If density increases what happens to volume?
When density increases, volume decreases.
