Physics Class 11 Short Notes, Study notes of Physics

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Ie PHYSICAL QUANTITIES AND MEASUREMENTS In this topic the examiner will test you on calculations involving physical quantities. The examiner expects you to know all the base quantities along with their units. The theory involving base quantities and derived quantities is also recommended for example speed is a derived quantity from the base quantity length and time. You should also be able to calculate errors and be able to figure out the dimensional analysis of quantities. For elaboration of topics look at the key concepts below Base quantities: The physical quantities in terms of which other physical quantities are expressed are known as Base quantities. Length, mass, and time are base quantities. Derived quantities: The quantities whose definitions are based on other physical quantities are known as Derived quantities, For example, definition of velocity base on time and displacement. Derived Units: SI units for measuring all other physical quantities are derived from the base and supplementary units, Quantity | Unit Symbol | Base Units Force Newton | N kgms~-? Work Joule J Nm=kg m?s? Power Watt W Jst=kg m? s3 Pressure Pascal Pa N m2=kg mts? Systematic/Random Errors Systematic: These are “reproducible” errors from faulty calibration or biased observation. They have the same magnitude and sign under the same conditions. Random: These are due to fluctuations in measurements from repeated experiments. They are caused by the fact that no two readings can be replicated in an experiment for instance measuring time for a runner to cover a lap. They have variable magnitude and a variable sign and can be minimized by repeating the experiment several times and taking the mean value. Absolute, fractional and Percentage Uncertainty For a quantity x = (2.0+0.2) mm e Absolute uncertainty: Ax = +0.2mm e Fractional uncertainty: = = 0.1mm e Percentage uncertainty: = * 100 = 10% Calculating uncertainty for a result involving measurements of several independent quantities