Ch 1Physical World — Class 11 Physics, concept-first.

Human beings have always been curious about the world they live in — the regular rising and setting of celestial objects, the change of seasons, eclipses, tides, volcanoes and rainbows have all provok…

Physics is conveniently pictured as spanning two domains. The macroscopic domain covers phenomena at laboratory, terrestrial and astronomical scales; the microscopic domain covers atomic, molecular an…

The links between physics, technology and society run in both directions. Thermodynamics as a subject arose directly out of the need to understand and improve heat engines, and the steam engine is ins…

We all carry an intuitive sense of "force" from everyday experience — the push needed to move an object, the impact felt when something hits us, the pull we feel on a merry-go-round.

The gravitational force is the mutual force of attraction between any two objects, purely by virtue of their masses.

The electromagnetic force acts between charged particles. When the charges are at rest, it reduces to the familiar Coulomb force — attractive between unlike charges, repulsive between like charges.

The strong nuclear force is what binds protons and neutrons together inside a nucleus. Some attractive force has to be doing this, because otherwise the electric repulsion between the positively charg…

The weak nuclear force shows up only in certain nuclear processes, the best known being -decay, in which a nucleus emits an electron together with an uncharged particle called the neutrino.

Unification is one of the recurring, deepest ambitions of physics (as noted in the opening section), and many of physics's greatest advances have been exactly this: showing that two phenomena that loo…

Physicists study everything from sub-atomic particles to the most distant stars, and beyond simply cataloguing facts by observation and experiment, they look for the underlying laws — usually written…