1. Pressure in a fluid Pressure in a fluid acts equally in all directions
Pressure increases with depth in a fluid
Pressure in a fluid also depends on the density of the fluid.
P=pressure
=density
h=depth

2. Mass and weight Mass is the amount of matter in an object.
Mass is measured in Kilograms
Mass is measured using a balance or scales.
Weight is the pull of gravity on an object.
Weight is measured in Newtons.
Weight is mass X acceleration due to gravity.

3. Archimedes Principle
Archimedes' principle states that the buoyant force on a body immersed in a fluid is equal to the weight of the fluid  displaced.
Explanation: an object weighs less in water. The reduction in weight equals the weight of water that is displaced.
Example: The weight of a block of wood is 4N. Its apparent weight when totally immersed in water is 1N. Calculate (i) the weight of water displaced (ii) the volume of the block (iii) the density of the wood.(density of water = 1000Kg/m3)

4. To Demonstrate Archimedes Principle
Note the weight of the object in air and water.
Weight the water that is displaced.
The loss in weight equals the weight of the water displaced.

5. The Law of Flotation…a special case of Archimedes principle
The weight of a floating object equals the weight of fluid displaced.

6. A ship displaces 2000m3 of sea water of density 1020Kg/m3
A ship displaces 2000m3 of sea water of density 1020Kg/m3. What is the mass of the ship?
A cube of metal of side 20cm weighs 500N. What does it weigh when in a liquid of density 800Kg/m3
A cube of wood of side 20cm, floats in a liquid of density 800Kg/m3 in such a way that 2cm of the block appears above the surface. What is the density of the wood.
Senior physics ch 7

7. Newton's law of universal gravitation
The force between 2 point masses is proportional to the product of the masses and inversely proportional to the square of the distance between them.
F=force of gravity
G=universal constant of gravitation
m= masses
d = distance