UNIT 1 JEE MAINS PHYSICS SI UNITS

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What is a unit?

Let us say you were to measure the height of the person. The answer wouldn’t be that the person is tall or short but the answer would be that the person is 160 centimeters tall or 200 centimeters tall or some other value depending on the height of the person.

Now we have compared the height of the person to centimeter and have counted how many times the person is to that of the centimeter. But what if the person height is to be given in Feet and Inches? You would simply compare the person’s height with that of Feet and Inches.

So measurement of any physical quantity with respect to the universally accepted reference is called as unit. Let us simplify this definition with the above given example. Here the physical quantity to be measured is the height. The universally accepted reference is the centimeter. Thus the reference centimeter is called as the unit.

We will return the result of the measurement of a physical quantity with a number followed by the unit.

Why should we use units?

In the above example if you say that the person is tall, then in your point of view the height of the person may be more than 160 centimeters but according to my point of view it may be above 150 centimeters. So if you say tall then I would consider 150 centimeters but according to your point of view it is 160 centimeters and there will be a sort of confusion between the two. But if you specify that the height of the person as 160 centimeters exactly then there will not be any confusion between both of us instead of using the word tall.

Units are further divided into Fundamental and Derived Units which we will be covering in the next tutorial.

There are many universally accepted units among different countries. Some of the well known unit systems are:

FPS: In FPS the measurement of length is done with Foot, mass with Pound, Time with Seconds.

CGS: In CGS systems length is measured in Centimeters, Weight in Grams, Time in Seconds.

MKS: In MKS length is measured in meters, mass in kilograms, time in seconds.

The system which is presently used and accepted is the SI unit. Full form of SI unit is Système Internationale. This is accepted universally and are used in industries and other places worldwide. They have adapted SI units as standard because it is easy to use and also it is easy to convert from this unit to others. It is to be remembered that we shall use SI units in all our tutorials.

UNIT 1 TUTORIAL 2 PHYSICS IN TECHNOLOGY AND SOCIETY

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We can say that technology and thus the society is always interconnected with physics. The present technology may not be directly connected with the physics but in some or the other way the basic principles used in the other way are directly related to physics. For example let us consider the computer you are using now. It has a chip which is made up of silicon and the study of the properties of this materials comes under the branch of physics called as material physics. Or for the sake of easy understanding let us consider the internet which you are using to study this document. In the earlier days there was not internet but telephone was introduced based on the basic laws of electricity and magnetism. That wired telecommunication gradually changed to wireless and finally we are not only communicating with other but also we are exchanging our data based on the laws of electricity and magnetism. Similarly the automobiles which are running on the roads are based on the laws of motion and energy from combustion of the fossil fuels. In similar way there are many examples which can be stated here but I think they are not very necessary as you know most of them. But I will give some data regarding some physicists from different countries of the world who have their major contributions to the subject of physics. Note that this data is not my original work but I have collected this from the NECERT textbook of INDIAN government of page number 5, 6 from Table 1.1. Picture quality is low as it is just for information.

Why I have started tutorials for JEE Mains and Unit 1 syllabus

When I have started this blog I thought of writing about fluid Mechanics but I have seen that there is a need for starting from basics so that if anyone gets doubt in basics then you guys can search about it and get the results. First I will start with the physics and continue to the other subjects so that this blog of mine will serve you very well. You can find our objectives of the first unit and the topics which will be covered in for the first unit here:

This is the unit 1 of the JEE mains and also the basics in physics. Let us have an approach which is different for learning and also useful for JEE mains.

Unit 1 – Physics and Measurement
Tutorial 1: What is Physics?
Tutorial 2: Technology and Society
Tutorial 3: SI Units
Tutorial 4: Fundamental and derived units
Tutorial 5: Least count
Tutorial 6: Accuracy and precision of measuring instruments
Tutorial 7: Errors in measurement
Tutorial 8: Dimensions of physical quantities
Tutorial 9: Dimensional analysis and its applications

Find the PDF of this unit here:

http://www.docdroid.net/file/view/xfty/unit-1.pdf