generally we can only observe the qualities of an object like its color smell taste hardness Etc but we cannot measure them so the observations we make for them are qualitative observations on the other hand the mass and volume of an object density of matter amount of energy increased or decreased Etc can be measured along with observations anything that can be measured is called physical quantity that is the mass of an object is a physical quantity but the smell is not a physical quantity the color of an object is usually not a physical quantity but the color of light when expressed as a wavelength then it is a physical quantity similarly length area time Etc are also physical quantities in physics one of the most important tasks is to measure these physical quantities as accurately and precisely as possible until a physical quantity is measured or expressed by means of a number and unit the observation does not complete so in this tutorial we are going to learn about the scientific ways of measuring these physical quantities so let's start [Music] [Applause] measurement is the very basis of all scientific studies and experiments it also plays an important role in our day-to-day life when it comes to building a table putting a picture on the wall timing a race we need to be able to do measurements because it answers questions such as how big how long how deep and how heavy The Things Are but to measure in a scientific way we need to know some basic aspects of measurement such as what is measurement what is physical quantity types of physical quantity what is unit types of units and the systems of units used in measurements what is measurement measurement is a process that is associated with physical quantities of Real World objects numbers units and various events it is very basic in engineering construction work medical or other technical fields and can be used for almost every activity in our daily life as we discussed earlier anything we measure is a physical quantity to measure a physical quantity we need two things one is the numerical value and the other is its unit for example the physical quantity length can be Quantified as 5 meters mass as 5 kilograms and time has 5 Seconds where 5 is the numerical value and meter kilogram and second are the units however in order to measure any physical quantity we have to follow some rules in the process of measurement We compare the given physical quantity with the known standard quantity of the same nature for the measurement of a physical quantity at first we consider a constant quantity of the same nature as a standard then we find the number which expresses how many times the standard quantity is contained in the given physical quantity for example the meter is the standard unit of length and 5 meters is five times the standard quantity of the length where the meter is the length of the path traveled by light in the vacuum during a time interval of 1 divided by 299 792 of a second types of physical quantity physical quantities can be classified into two categories base quantity and derived quantity base quantity base quantities are independent physical quantities which help to obtain and find other physical quantities examples of such quantities are length mass time electric current temperature amount of substance and luminous intensity derived quantity derived quantities are such quantities that are derived from the combination of Base quantities through multiplication and division only no addition or subtraction or any other sign for example area is a derived quantity because it is measured by multiplying length by length similarly volume as length into length into length and also density is measured as the mass of the object divided by its volume there are many such derived quantities that we will face later for now here is a small table showing some derived quantities and the relation with base quantities what is unit is the quantity of a constant magnitude that is used to measure the magnitude of other quantities of the same nature as in the example above meter is used as the unit of a constant magnitude for length similarly kilogram is used for mass and second for time but to accept any unit internationally we need to be followed three essential conditions it should be possible to define the unit without ambiguity the unit should be reproducible and the value of the unit should not change with space and time types of units like physical quantity units are also two kinds base units and derived units base units base units are independent units which help to obtain and find other units these units can neither be changed nor can be related to any other base units for example the units of length mass time electric current temperature amount of substance and luminous intensity derived units derived units are those units that depend on the base units or can be expressed in terms of the base units for example the unit of area volume density Force Etc systems of units basically for a long time three types of unit systems have been used all over the world these systems of units are CGS or centimeter gram second MKS or meter kilogram second and FPS or foot pound second the CGS unit system this is a French unit system in this system the unit of length is centimeter the unit of mass is gram and the unit of time is second the MKS unit system this system of units is also known as the metric system of units in this system the unit of length is meter the unit of mass is kilogram and the unit of time is second the FPS unit system this is a British unit system in this system the unit of length is foot the unit of mass is pound and the unit of time is second International System of Units or SI unit system the SI unit system is the modern form of the metric system this system was established by the supreme authority of the international Bureau of weights and measures basically it was designed to replace the misunderstood and mixed up units that were in use at that time this unit system is the world's most widely used system of measurement today scientists all over the world use this unit system for communicating with the international scientific community the SI unit system comprises a coherent system of units of measurement starting with seven base units which are meter to unit of length kilogram the unit of mass second the unit of time mole the unit of the amount of substance Kelvin the unit of temperature ampere the unit of electric current and Candela the unit of luminous intensity if you enjoy our videos then don't forget to like share and subscribe