WHAT IS PHYSICS
Physics is one of the branches of science that deal with properties of matter in all its states, Energy in all its forms, and the relationship between matter and energy.
PHYSICAL QUANTITIES
DEFINITION: The quantity that is measured is called physical quantity.
Example: length, mass, time.
The quantity which is not measurable is not a physical quantity.
Example: Idea, dream, small, color.
There are two types of physical quantities:
1. Fundamental physical quantity
2. Derived physical quantity
Fundamental physical quantity: Physical quantities that are independent or on other are called fundamental physical quantities.
Example: Length, mass, time.
Derived physical quantity: The physical quantity which are from the fundamental physical quantity is called derived physical quantity.
Example: Area, volume, speed, density.
Units: The standard that is used to measure a physical quantity is called a unit.
CHARACTERISTICS OF UNITS:
1. It should be well defined with ambiguity.
2.. It should be a convenient size.
Fundamental units
The units that are used to measure fundamental physical quantities are called fundamental units.
Example: meter, kilogram, second.
Derived units: The units that are used to measure derived physical quantities are called derived units.
System of units
There are 3 systems of units for measuring the physical quantities are
1. CGS system
2. FPS system
3. MKS system
ADVANTAGES OF S.I UNITS:
1. The base and supplementary units cover all branches of science and technology.
2. All the units are well-defined without any ambiguity.
3. All the units are easily reproducible.
4. All the derived units can be obtained by simple multiplication and or division of fundamental units.
5. These are special names for some difficult and familiar derived units.
6. There are multiples, submultiples, prefixes, and symbols to express large and smaller values.
7. Almost all countries have adopted the S.I system.
DIMENSIONS
The dimensions are the powers to which the fundamental units are to be raised to represent a derived unit.
APPLICATIONS OF DIMENSION ANALYSIS:
1. One system unit can be converted into another system.
2. The correctness of the equation can be checked.
3. Equation connecting different physical quantities can be derived.
LIMITATIONS OF DIMENSIONAL ANALYSIS:
1. The dimensional constants and proportionality constants cannot be determined by this method.
2. This method is not applicable if an equation contains trigonometric exponential and logarithm functions.
3. It is difficult to use this method if a physical quantity depends on more than three other physical quantities.
4. If a physical quantity is the sum of difference or two or more other physical quantities, dimensional analysis is not useful to derive the relationship among them.
5. Numbers and dimensions less quantities cannot be determined by this method.
6. In some cases the proportionality constant also possesses dimensions. in such cases, it is difficult to interfere with the physical quantities involved in them and hence the dimensional analysis is not useful.
ERRORS
DEFINITION: The amount of deviation from the exact value is called an error.
EXPLANATION: The error may be positive or negative if the measured value is less than the actual value. The error is negative the measured value is greater than the actual value. The error is positive.
ABSOLUTE ERROR: The difference between the measured value of a quantity and its actual value is called absolute error.
EXPLANATION: The absolute error tells about much exactly the measured value differs from the actual value in other words it is the difference between what should be measured. It is a non-negative value and hence the modules of the differences are to be considered.
RELATIVE ERROR: The ratio between the absolute error and the actual value is called relative error.
The relative error tells whether the error of the measured value is big or small compared to the actual value. The relative error is high when the absolute error is high. The relative error has no units.
PERCENTAGE ERROR: The specific amount of absolute error that occurred as a fraction of a hundred is called a percentage error.
EXPLANATION: Percentage error is a calculation of the percentage of the absolute error in measurement this is also equal to a hundred times relative error. If the percentage error is small, then the measured value has no units.
SIGNIFICANT ERROR: Significant figures are the number of digits in a value that gives information about the accuracy of a measurement.
EXPLANATION: Significant figures are the important digits of a number that are used to express it to the required degree of accuracy, in other words, the number of significant figures.
VECTORS
Vectors are two types:
1. Scalar quantities
2. Vector quantities
SCALAR QUANTITIES: The physical quantity which possesses only magnitude but no direction is called scalar quantity or simple scalar.
EXPLANATION: Suppose that the length of a straight line is 20cm is the magnitude of the length and this quantity is not having direction.
VECTOR QUANTITIES: The physical quantity which possesses both the magnitude and direction and obeys vector law is called vector quantity or simple vector.
EXPLANATION: The displacement is the change in position in a particular direction change in position gives the magnitude and the direction in which the body displaced fulfills the requirement of a vector.
TYPES OF VECTORS:
PROPER VECTOR: The vector whose magnitude is not wqual to zero is called proper vector.
NULL VECTOR: The vector whose magnitude is zero is called null vector.
UNIT VECTOR: The vector whose magnitude is unity is called unit vector.
EQUAL VECTOR: The vector having same magnitude and same direction are called equal vectors.
NEGATIVE VECTORS: The vertex having same magnitude and in opposite direction to given vector is called negative vector.
LIKE VECTOR: The vector having same direction inespective of their magnitudes are called like vectors or co-directional vectors.
CO-INTIAL VECTOR: The vector having same intial point irrespective of their magnitudes and directions are called co-intial vectors.
RESOLUTION OF VECTOR
The process of splitting a vector is called the resolution of the vector. It is convenient to resolve a vector into two components which are right angles to each other in a rectangular coordinate system then the components are called rectangular components.
