Form 1
1.3.5 Density/relative densityMass - 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 forceForce - 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 forceTypes 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 forcesEffects 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 principleArchimedes 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 FlotationFlotation - 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