Mechanics

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¹ In physics we often call a particle “slow” if its velocity is “small” compared to the speed of light.

²This term is used mostly in quantum mechanics.

³The adjoint “gee” stands for the earth, “helion” for the sun. “peri” stands for near, and “ap” for far. For a general elliptical trajectory a proper term could perhaps have neen periapsis for the nearest point and apapsis for the furthest point. However, many authors use both the terms “perihelion” and “perigee” for the nearest point, not only for an elliptical orbit, but also for a hyperbolic orbit. We shall use the terms “perigee” and “apogee” for all orbits, elliptical as well as hyperbolic. See Goldstein, Classical Mechanics, 2nd Ed., Narosa, New Delhi (1989), page 98.

⁴At infinity the ...