Section 1.8 Chapter Summary
Physics attempts to explain all natural phenomena on all length and time scales. Natural phenomena and experiments guide physicists and help them develop better understanding of the world. Introductory physics is divided into classical and modern physics. Classical physics includes Newtonian mechanics, gravitation, fluids, waves, sound, thermodynamics, electricity, magnetism, and light. Modern physics includes special relativity and quantum mechanics, and their applications. Although physicists work in specialized branches of physics, they have a common approach and similar training.
Physics is an empirical science and measurements in experiments or observations on natural phenomena are essential for unlocking the mysteries of nature. The measurements of physical quantities are expressed in comparison with standards which define units. The units for the three fundamental quantities in the present international system of units, called the SI units or the metric units, are length (meter), time (second), and mass (kilogram).
Measurements are always accompanied by uncertainties. The value of a measured quantity is given by its average value and an uncertainty. The precision in measurements refers to the repeatability of the outcomes reflected in closeness of the measured values for different trials. Based on the precision of the experiment, measured quantities are written to appropriate number of digits of significance, called significant figures. The scientific notation allows one to express significant figures unambiguously. In a scientific notation a decimal number between 1 and 10 multiplies a power of ten. Significant figures in the scientific notation are indicated by writing the decimal number up to appropriate digits.
The order of magnitude estimates are important in physics. The order of magnitude for a physical quantity estimations are made using general principles, approximate relations and reasonable expectations.
The dimensional analysis can be used to check the correctness of a physics equation and to make reasonable guesses about the dependence of a physical quantity on other quantities.
