1. Density  = m ÷ V  - rho Density = mass ÷ volume Density is measured in kg/m 3 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.

2. 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

3. Solidliquidgas Density 100010001 Volume 111000 Spacing 11 10

4. Pressure Pressure = force ÷ area P = F ÷ A Pressure is measured in N/m 2. It is a scalar quantity. 1 N/m 2 = 1 Pascal = 1 Pa Which would sink into mud further? weight

5. Pressure

6. 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.

7. 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.

8. F B- buoyancy F w - weight FwFw FBFB FwFw FBFB F u = F B + F w if F B = - F W object is stationary F u = F B + F w if F B > - F W object is rises F u = F B + F w if F B < - F W object is sinks Floating or Sinking F B – F w is sometimes called the apparent weight

9. 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

10. 1.An object with mass 0.5 kg and density 4000kg/m 3 is totally immersed in water. Water density 1000 kg/m 3 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