Physical World - Revision Notes
CBSE Class 11 PHYSICS Revision Notes CHAPTER 1 PHYSICAL WORLD 1 Physics-Scope and Excitement 2 Physics, technology and society 3 Nature of physical laws There are four fundamental forces which govern both macroscopic and microscopic phenomena. There are (i) Gravitational force (ii) Nuclear force (iii) Electromagnetic force (iv) Weak force The relative strengths of these forces are F g : F w : F e : F s = 1: 10 25 10 25 : 10 36 10 36 . 10 38 10 38 All those quantities which can be measured directly or indirectly and in terms of which the laws of physics can be expressed are called physical quantities. (a) Fundamental quantities (b) Derived quantities. The units of the fundamental quantities called fundamental units , and the units of derived quantities called derived units. System of units:- (a) MKS (b) CGS (c) FPS (d) SI The dimensions of a physical quantity are the powers to which the fundamental quantities are raised to...