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# Physics and Measurement

## Physics and Measurement PDF Notes, Important Questions and Synopsis

SYNOPSIS

• Physics domain:
1. Macroscopic domain: This includes phenomena at the laboratory, terrestial and astronomical scales. Classical mechanics deals with the macroscopic domain.
2. Microscopic domain: This includes atomic, molecular and nuclear phenomena. Quantum mechanics deals with the microscopic domain.
• Four fundamental forces of nature:
 Force Relative strength Range Gravitational force 10-39 Infinite Nuclear force (weak) 10-13 Very short, sub-nuclear size Electromagnetic force 10-2 Infinite Nuclear force (strong) 1 Short,  nuclear size
• Physical quantities:

• Measure of physical quantity (Q) = numerical value of physical quantity (n) × size of unit (u) n1u1 = n2u2 = constant

• Fundamental quantities, SI unit and their symbols:

 Fundamental quantity SI unit Symbol Length metre m Mass kilogram kg Time second s Electric current ampere A Temperature kelvin K Amount of substance mole mol Luminous intensity candela cd
• Conversion of units:
Consider dimensions of a physical quantity as ‘x’ in mass, ‘y’ in length and ‘c’ in time. If the fundamental units in one system are M1, L1 and T1 and in another system are M2, L2 and T2
then

• Analysis of dimensional correctness:
Every equation should be dimensionally balanced. This is called ‘principle of homogeneity’. The dimensions of each term must be the same on both sides of the equation.
• Principle of homogeneity:
According to the principle of homogeneity, dimensions of all terms in a physical expression should be the same.
• Errors:
Errors are classified as (i) systematic errors and (ii) random errors.
• If x1, x2, x3 … xn are the measured values of quantities in several measurements, then the mean is

• Absolute errors in measured values are
• If the quantity Z is expressed as a product of quantities A and B, then the maximum fractional error in Z is given by
• If Z = AxByCz, then the maximum fractional error in Z is

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