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1.3.5 Density/relative density

Mass - The quantity of matter in a body. The SI unit is kg

Volume - The amount of space occupied by a substance. The SI unit is m3, for liquids it is litres (l)

Weight - It is the attractive force towards the earth’s center exerted by the earth on the body. Its SI unit is N

Density - The ratio between the mass of an object and its volume

Relative Density - The ratio of the density of a substance to the density of water

Specific Gravity (Relative Density) - The ratio of the density of a substance to the density of a given reference material (i.e. water)

Hydrometer - An instrument used to measure the specific gravity (or relative density) of liquids

1. In an experiment using a Hare’s apparatus, the lengths of a methanol column and a water column were found to be 16 cm and 12.80 cm respectively 1.4.0 Force 1.4.1 Concept of force

Force - Any influence that causes a free body to undergo acceleration

Weight - The product of mass times the weight of gravity (W = mg)

1.4.2 Types of force

Types of force - Attractive force, tortional force (torque), stretching (elastic) force, compressional, repulsive, frictional force

Attractive Force - A force which brings one object towards another

Torque - A force which twists or rotates an object

Elastic Force - A restoring force that returns a body to its original shape

Compressional Force - A force which puts pressure on an object which decreases its size

Repulsive Force - A force which pushes to magnets apart (ex north pole and south pole)

Frictional Force - A force which prevents a body from sliding, opposes its movement

5 1.4.3 Effects of forces

Effects of forces - Changes the speed of an object, changes the size or shape of an object, changes the direction of movement of an object

1.5.0 Archimedes principle and the law of flotation 1.5.1 Archimedes principle

Archimedes Principle - When a body is partially or totally immersed in a fluid it experiences an upward thrust which is equal to the weight of the displaced fluid

Upthrust - The force exerted by a liquid to a body when the body is partially or totally immersed in water

Opposing forces acting on an object which is totally submersed in water - Upthrust, weight of the object

1.5.2 Law of Flotation

Flotation - A special case when the upthrust is big enough to equal the weight of the object

Law of Flotation - A floating body displaces its own weight of the fluid in which it floats



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