Physics 1st Paper · Classes 11-12 · Chapter 1 · 1.1 to 1.2

Nature of the Physical World and Scope of Physics.

A brick and a mango tree are both part of the world, yet physics files them in different places. Not by size, not by material, but by one question: does it have life? We start there and end among the eight branches of physics.

1. The world and its two halves

Whatever exists, meaning mass and energy, is the world. It makes no difference whether we sense it with our five senses or it lies beyond them.

The world splits in two. Things without life make up the physical world: brick, stone, iron, gold, soil. Things with life make up the living world: humans, cows, goats, plants. Drop the chips into their boxes and see.

The physical world is built from four components: space, time, mass and energy. Space and time are theoretical, so “physical world” really means the presence of mass and energy. Einstein’s formula E = mc² ties those two together.

Try E = mc² with your own hands. Turn mass into energy first through classical eyes, then through Einstein's.

The discussion of special knowledge about the many aspects of the physical world is physical science. That knowledge is still small: of all the matter in the world, humans have come to know only 4%. Look small and a body breaks into molecules, and molecules into atoms. Look large and you find satellites, planets, the solar system and galaxies.

Travel the smaller and the bigger view yourself. Go down from a brick to a fundamental particle, and up to the farthest sky.

2. The branches of physics

Physics is the key to science. It is the fundamental branch of the other sciences, because its principles form the basis of the rest. It is divided into eight parts: general physics, heat, sound, light, magnetism, electricity, electronics and atomic physics.

General physics has two parts: mechanics and properties of matter. Mechanics has two parts as well. Statics studies the action of force on bodies at rest; dynamics studies it on bodies in motion. Dynamics divides again into kinematics and kinetics. Open the tree one level at a time.

The eight branches don't only live in the book's tree. They're in your room too. Go and find them.

Properties of matter come in two kinds too. A property found in all matter to some degree is a general property: weight, extension, resistance, elasticity. A property not found in all matter is a special property: rigidity and fragility belong to solids only, viscosity to liquids and gases, surface tension to liquids.

3. Physics in daily life

Thanks to physics, calling the modern age the electrical age is no exaggeration. The instruments of weather are its gift too: a barometer measures air pressure, a thermometer measures temperature, a hygrometer measures the amount of water vapour in air. And thanks to science we can observe from fundamental particles of size 10⁻¹⁵ m out to skies at a distance of 10²⁵ m.

4. Check yourself

The first question is about the very foundation of this page.

In the second, recall how the branches relate.

The third is about general and special properties.

The whole note on six cards.

Source: Physics 1st Paper, Classes 11-12 (NCTB), Chapter 1 “Physical World and Measurement”, section 1.1 to 1.2.