Tiêu đề PHYSICS PART- 1.pdf ✅

PHYSICS Class - C5 (Part - I) 1) UNITS AND DIMENSIONS - I WISE UP Science is what people know about the world and the life that is on it. The land, the ocean, the weather, the stars, the medicines, the plants and the animals are all the parts of science.
The word physics is taken from the Greek word physikos, meaning nature. However, it does not mean that all sciences which deal with nature are classified as physics. Broadly speaking, physics is a branch of science which deals with the study of matter and energy under various situations. Physics can be defined as the study of phenomena which are taking place in matter and energy. Length, Mass, Time are basic measurements. Length : Length is the measure of distance between two points.
Mass : Mass is the amount of matter contained in a substance. Matter is made of molecules. In certain substances these molecules are more tightly packed, as compared to other substances. The total amount of matter of these molecules present in a given substance gives us the idea of mass. For finding the mass of substances in general, just as at grocer's shop a simplified form of physical balance. Time : Time is defined as a gap between two events. Solar day : The gap between two successive noons is called solar day. Mean solar day : The average of all solar days in which earth completes one revolution around the sun is called mean solar day. Area : The amount of surfáce occupied by an object or a place)s called its area. Volume : The space occupied by a substance) solid, liquid or gast is called volume. Density : The mass per unit volume of a substance) is called density. Imagine that you have an aluminium cube of volume 20 cm3 . If it is weighed on physical balance, then its mass is 54 g. Now we can say . 20 cm3 of aluminium has mass = 54 g ∴ 1 cm3 of aluminium has mass = 54 g 20 cm3 = 2.7 g cm3 or 2.7 g cm−3 As the mass per unit volume is the density.
Weight : Weight is the force with which the earth pulls a body towards its centre.) The weight is generally measures in kilogram - force (kgf) or gram - force (gf) with the help of a spring balance. 1kgf = 9.8 N; 1gf = 980 dyne) CONCEPT - I QUANTITY : Quantity means size, amount, vastness, magnitude or simply stated as the answer for Kow much?' or 'how many?') PHYSICAL QUANTITY : A Quantity which can be 'measured' is called physical quantity. Example : Length, Area, Volume, Speed, Force, Energy etc. Physical quantities are organised into various ways invarious systems like FPS, CGS, MKS and SI . Now the scientists of all the countries are following SI for all their research work. In SI, physical quantities are organised into three groups. They are: • Fundamental physical quantities • Supplementary physical quantities • Derived physical quantities SET OF FUNDAMENTAL PHYSICAL QUANTITIES : Consider a set of physical quantities. If no quantity can be derived from the remaining physical quantities, then the set is called set of fundamental physical quantities.).