## units and measurements notes

(i) acceleration Dronstudy provides free comprehensive chapterwise class 11 physics notes with proper images & diagram. (i) The metre (m) - standard of length Players may score points but can never win -, An untested speculation for the status of, Any hypothesis, law or theory may be challenged by any player at any time. The metre (m): This is defined as 1650763.73 times the wavelength, in vacuum of the orange light emitted by  in transition from 2p10­  to 5d5. The standard unit should be easily made available for comparing with other quantities. [v] = {[r]^a}{[\rho ]^b}{[\eta ]^c} These units are called derived units. Angstrom (Å)  = 10-10 m In electricity and magnetism a standard for current is required in addition to the three base units of mechanics. D = density of medium. Often derived units are given names. var h = now.getHours(); The standard unit should be easily made available for comparing with other quantities. The common system of units which is used in mechanics are given below: 1. Unit of force in cgs = g cm s-2 In Physics, we consider units of measurement of mass, length, and time as the fundamental units and these units represent our basic scientific notations. Units of all other quantities may be obtained by some combination of the base units. The interval is divided into 273.15 divisions and each division is taken as unit temperature. [L. H. S.] = \left[ {{{A\,Number} \over {Time}}} \right] = {1 \over T} = {T^{ - 1}} 1. The value of a force on a body is 20 N in SI units. System of units For example, the formula of area = length * length = m * m = m 2. The number thus obtained is known as the magnitude and the standard chosen is called the unit of the physical quantity… Symbolically, dimension of a physical quantity is written by putting that physical quantity within bracket such as [A] and it is read as dimension of A. (ii) v = \sqrt {{P \over D}} , where v = velocity of sound   and P = pressure. [L. H. S.] = [t] = T.   Hence the relation is correct. Are you looking for reliable and easy-to-comprehend notes of physics class 11 chapter 2 for your exam preparation? This standard is called the unit of that physical quantity. (ii) angle The Kelvin (K): In SI units, temperatures are measured on the thermodynamic scale with absolute zero as zero and the triple point of water (i.e., the temperature at which ice, water and water vapour are in equilibrium) as the upper fixed point. (b)  Availability To measure a physical quantity, we have to find out how many times a standard amount of that physical quantity is present in the quantity being measured. A newly born theory should not only explain experimental facts already established but also predict some new facts. All disputes will. The dimension of a physical quantity are the powers of  the fundamental quantities to which they are to be raised to represent a unit of that physical quantity. s = checkTime(s); This notes is very nice and in easy language for study. Vedantu provides the best-rated CBSE study materials for all classes. n = 20\left( {{{kg} \over g}} \right)\left( {{m \over {cm}}} \right){\left( {{s \over s}} \right)^{ - 2}} = 20\left( {{{1000 g} \over g}} \right)\left( {{{100 cm} \over {cm}}} \right) This unit is called the Kelvin. Assuming that the critical velocity of flow of a liquid through a narrow tube depends on the radius of the tube, density of the liquid and viscosity of the liquid, find an expression for critical velocity, Class 9 - Science+Maths Video Paper Solutions, Class 10 - Science+Maths Video Paper Solutions, 11+12 - Physics + Chemistry + Mathematics, 11+12 - Physics + Chemistry + Mathematics (IIT), 11+12 - Physics + Chemistry + Biology (NEET), Class 9th and 10th : Foundation for IIT Physics, Class 9th and 10th : Foundation for IIT Chemistry, How to make the best choice: Science vs Commerce vs Arts, How to Study Effectively- 9 Secrets No One Tells, How to prepare for IIT-JEE this summer - Top 7 proven ways.