 |
Introduction |
| |
Humans have always been curious about the world around them. The world has an astonishing variety of materials and bewildering diversity of life and behaviour. The inquiring and imaginative human mind has responded to the wonder and awe of nature in different ways. This human endeavour led, in course of time, to modern science and technology. |
|
What is Physics? |
| |
The word 'Physics' comes from the Greek word 'phusis' meaning 'nature', introduced by the ancient scientist 'Aristotle'. Man has always been fascinated by nature. So, he questioned and sought answers for every phenomena nature could offer. The branch of science which is devoted to the study of nature and natural phenomena is called Physics. It is expected that all the events in nature take place according to some basic laws. Physics reveals these basic laws from day-to-day observations. |
|
The Basic Forces in Nature |
| |
The gravitational force is inversely proportional to the square of the distance between the two bodies and directly proportional to the product of the masses of two bodies. |
|
Laws of Conservation |
| |
There are nearly 14 laws of conservation based on symmetry principles in physics. Anything that happens must not be forbidden by a conservation law. |
|
Summary |
| |
The laws, formulae and calculations of physics are not merely things to be remembered from the point of view of exams, but their knowledge increases your interest in matters of everyday life. |
|
Introduction - Systems of Units |
| |
A unit of a quantity is the standard quantity used to measure a physical quantity. |
|
Need of Measurement and System of Units |
| |
Before all the branches of science were clubbed together under the nomenclature 'Natural philosophy', under which all observations of subjective nature were being carried out and spirit of enquiry was almost non-existent, we were satisfied with simple explanations. |
|
Mass |
| |
In 1967, the atomic clock was adopted, choosing caesium-133 atom, which emits electromagnetic radiation of a precise and unvarying frequency, corresponding to the transition between two hyperfine levels of the ground state. |
|
Abbreviations in Power of 10 (Used in SI units) |
| |
Prefixes are used for large and small quantities. The following table gives prefixes, their symbol and their values in powers of 10 used in SI units. |
|
Order of Magnitude |
| |
Order of magnitude of a quantity is the power of 10 of the number that describes the quantity. |
|
Introduction - Physical world and Measurement |
| |
Physics is sometimes called as 'science of measurement'. The acceleration produced by a force for the motion of a body can be known by measuring the magnitude of applied force and mass of the body. |
|
Atomic to Astronomical Range of Variation of Length |
| |
Some objects have a wide range of lengths in the universe. |
|
Length Measurements |
| |
It is the shortest distance between two ends of the body. For measuring lengths, two methods can be employed, namely direct method and indirect method. Direct methods are employed for measuring small lengths by comparing such lengths or distances with an approved standard of length viz. vernier callipers, screw gauge and so on. For long, atomic and astronomical distances, indirect methods are used. |
|
To Calculate the Radius of Atom by Making Use of Avogadro's Hypothesis |
| |
By Avogadro's hypothesis, the actual volume occupied by the atoms in one gram of a substance is 2/3rd of the volume occupied by 1 gram of the substance. |
|
To Determine Molecular Size |
| |
A solution of known concentration of oleic acid in alcohol is prepared. |
|
Determination of Diameter of Moon |
| |
Let moon be the astronomical object of diameter D. Let E be the point on earth's surface. |
|
To Determine the Height of an Accessible Electric Pole |
| |
Let AB be an electric pole, standing upright, on the ground. Let the point C be the observation point i.e., the observer standing. |
|
To Determine the Height of an Accessible Tree using a Sextant |
| |
AB and CD are two mirrors fixed, as in the diagram, parallel to each other and facing each other, i.e., the reflection on CD is seen on AB. A small telescope and a vernier travelling over a scale, graduated in degrees, constitute the sextant. |
|
To Determine the Height of an Inaccessible Mountain |
| |
Let PQ be the symbolic representation of the mountain (h), inaccessible for direct measurement. Let A and B be two points of elevation subtending angles q1 and q2 of the top of the mountain at P. |
|
To Determine the Width of a River |
| |
PQ, the width of the river= W. AB, the known distance= x |
|
To Measure the Distance of a Submarine (Echo Method) |
| |
Ultrasonic waves are transmitted through the ocean and if on its path any submerged objects are encountered, then as per law, the waves are reflected back to the origin. |
|
Measurement of Mass |
| |
It is the mass of a body measured, when it is in translatory motion, by the application of external force other than gravity. |
|
Introduction - Significant Figures |
| |
Measuring instruments have a limit upto which measurements can be made, called as the least count of the instrument. Errors are seen when measuring through various instruments. |
|
Significant Figures |
| |
It is the expression of accuracy of a physical quantity. The value in digits, accurately known in a measurement plus one digit that is not certain, is called significant figures. Significant figures is directly proportional to the accuracy of measurement. |
|
Arithmetic Operations With Significant Figures |
| |
The accuracy of a result is taken to be equal to the least accurate among the numbers, when 2 or more numbers are used to add, subtract, multiply or divide. The number of significant figures in the result, is equal to the number of significant digits in the least accurate one among them. |
|
Propagation of Errors |
| |
Final result of an experiment is calculated from a number of observations taken from different instruments, connected through a formula. |
|
Summary |
| |
The accuracy of a measuring instrument depends upon the least count of the measuring instrument. |
|
Fundamental and Derived Units |
| |
The units of fundamental physical quantities are called fundamental units. They are length, mass and time. These units can neither be derived from one another nor can be resolved into any other units. They are independent of one another. |
|
Dimensional Formulae and Dimensional Equation |
| |
It is the term which tells about the power with which a fundamental quantity is contained in a physical quantity. |
|
Principle of Homogeneity of Dimensions |
| |
It states that if the dimensions of each term on both the sides of equation are same, then the physical quantity will be correct. |
|
Limitations of Dimensional Analysis |
| |
If a quantity is dependent on trigonometric or exponential functions, this method cannot be used. |
|
Four Categories of Physical Quantities |
| |
Based on dimensions, physical quantity can be classified under four categories. |
|
Advantages of Dimensional Analysis |
| |
Dimensional equations are used to validate the correctness of a physical equation. |
|
Conclusion |
| |
This completes the five chapters under Unit-1 which has taught all those items (such as bricks, mortar, stores, etc., needed for construction of a house) which are the building blocks for observing, studying, understanding and developing the knowledge of science in general and physics in particular, for laying a proper foundation to achieve the happiness of humanity at large. Hope the presentation loads for better interest in pursuing the course of physics further. |
