Density = m ÷ V - rho Density = mass ÷ volume Density is measured in kg/m 3 or kgm -3. It is a...
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Transcript of Density = m ÷ V - rho Density = mass ÷ volume Density is measured in kg/m 3 or kgm -3. It is a...
Density
= m ÷ V - rho
Density = mass ÷ volume
Density is measured in kg/m3 or kgm-3.
It is a scalar quantity ( mass and volume are both scalar)
Density - to do with the mass of each atom and how tightly they are packed together.
Each material has its own density which can be used to identify it.
You have 4 activities to do
the density of a solid
the density of a liquid
the density of a gas (air)
how the density of solids liquids and gases compare
Tutorial questions Density Qu 1 to 9
SAQs 90 to 93
Purple book Chp 3.1
Solid liquid gas
Density 1000 1000 1
Volume 1 1 1000
Spacing 1 1 10
Pressure
Pressure = force ÷ area
P = F ÷ A
Pressure is measured in N/m2. It is a scalar quantity.
1 N/m2 = 1 Pascal = 1 Pa
Which would sink into mud further?
weight
weight
Pressure
Example: Explain why a person can lie on a bed of nails but can’t on a single nail.
Note: it is good to use an equation in an explanation
Experiment A: Find your pressure on the floor when you stand on one foot.
Experiment B: Find out how a liquid’s pressure varies with its depth
Experiment C: Find out how pressure of a liquid varies with its density
Tutorial questions 10 to 14
Examine a Bourdon Gauge and draw a labelled diagram of it.
From the previous experiment
P = gh where h is depth
Pressure increases with depth
Sidewise forces cancel out.
Up force due to water pressure is bigger than downward force.
F = PA
Upthrust or buoyancy is the difference in the upward and downward forces.
Buoyancy equals the weight of the displaced liquid.
FB- buoyancy
Fw - weight
Fw
FB
Fw
FB
Fu = FB + Fw if FB = - FW object is stationary
Fu = FB + Fw if FB > - FW object is rises
Fu = FB + Fw if FB < - FW object is sinks
Floating or Sinking
FB – Fw is sometimes called the apparent weight
For balanced forces there is no change in movement.
Force due to water - buoyancy
Force due to gravity - weight
Going down Decrease weight Going up
Increase weight
1. An object with mass 0.5 kg and density 4000kg/m3 is totally immersed in water. Water density 1000 kg/m3
What is(a) its volume(b) the apparent weight.
2. A hot air balloon is tethered to the ground. Draw a free body diagram showing the forces on it.
SAQ pages 20 to 26
Purple book Chp 3.8
3. Calculate the apparent weight of a 1kg mass of volume 150ml.
Then try it out.
Tutorial questions 15 to 20