《大学物理》英文课件1 Measurement幻灯片课件.pptVIP

Measurement Dr. Huaqiu Deng E-mail: hqdeng@scut.edu.cn 1-1 Measuring Things What is physics? - We discover physics by learning how to measure the quantities involved in physics. - Physics is based on measurement and experiment. Measure physical quantity in its own units, by comparison with a standard. Pick out a small number of physical quantities, and assign standards to them alone. Define all other physical quantities in terms of these base quantities and their base standards. International System of Units (SI) (metric system) Quantity Unit Name Unit Symbol Length meter m Time second s Mass kilogram kg 1-2 The International System of Units Factor 109 106 103 10-2 10-3 10-6 10-9 10-12 Prefix giga- mega- kilo- centi- milli- micro nano- pico- Symbol G M k c m μ n p 1-3 Changing Units A standard meter bar in Paris A wavelength of a particular light The meter is the length of the path traveled by light in a vacuum during a time interval of 1/299792458 of a second, so the light speed is exactly. 1-4 Length