AY 102 Lecture Notes - Lecture 3: Radiant Energy, Thermal Energy, Kinetic Energy
29 Jan 2018
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Ne(cid:449)ton"s uni(cid:448)ersal la(cid:449) of gra(cid:448)itation, telescopes, intro to physical concepts. One of four fundamental forces of nature: strong nuclear force (holds atomic nuclei together; very short ranged, weak nuclear force (involved in radioactive decay, electromagnetism (acts between charged particles; 0. 01 times strong nuclear force, gravity. Although gravity hold the earth together and keeps our feet on the ground, it does not hold our bodies or everyday small objects together. The universal law of gravitation: every mass attracts every other mass, attraction is directly proportional to the product of their masses, attraction is inversely proportional to the square of the distance between their centers. Weightlessness occurs when an object is in freefall, as in orbiting spacecraft or skydiving. An orbiting object in freefall accelerates towards the earth but never reaches the ground due to the fast, sideways motion. The sideways speed of a skydiver is not fast enough to avoid reaching the ground.
