Conceptual Physics Study Notes & Questions: Relativity (Chap. 28)

1. Conceptual Physics Study Notes & Questions: Relativity (Chap. 28) • Your frame of reference is the physical surroundings from which you observe and measure the world around you. For the most part, you are stationary with respect to it. For example, the interior of an airliner at 35000 feet, traveling at 600 mph (relative to the ground), is stationary to you—it is your frame of reference (p604). • The principle of relativity: every observer must experience the same natural laws (p606). For example, if you measure the speed of light in your airliner, you would measure the same speed as when you were on the ground; as when you were traveling at 185,000 mile per second (99.5% the speed of light!). The speed of light in a vacuum, c, is the same in all frames of reference. • Special relativity deals with frames of reference traveling at uniform motion relative to one another (p606). General relativity deals with any frame of reference, whether it is accelerating or not. • The Lorentz factor, f, is a key factor in special relativity • f = sqrt( 1 – v2/c2 ) £ 1 • If you observe an object traveling at a speed v relative to you: • The rate of time, R, on the object appears slowed to fR • The length of the object, L, is foreshortened to fL • The apparent mass of the object, M, is increased to M/f • E = mc2 there is a whole lot of energy bound up in mass. Energy can be released through nuclear reactions that convert some portion of subatomic mass into energy (p615). • In general relativity, acceleration due to gravity is indistinguishable from an acceleration frame of reference (p615). • Gravitational field “bend space-time”, which causes light rays to bend, and time to slow in intense G fields (p617). • In black holes, the force of gravity is so intense even light can not escape (p619).