PHYS114 Lecture Notes - Lecture 7: James Prescott Joule, Space Debris, Sept
Document Summary
The law of the conservation of energy: the sum total of energy in a closed system never changes, we never see energy, only its effects, energy can only change form. James prescott joule: experimented with electrical currents, came up with the idea of conservation of energy, contributed to thermodynamics. Momentum: a vector, p = mv, always conserved in an isolated system, objects exchange momentum via equal and opposite forces, types of collisions - elastic and inelastic. Too shy to publish his results: used a torsion wire (a twistable wire). Measure how much it is twisted and how much force is required to twist it. If fg = gmm/r2, and fg = gm, then gm = gmm/r2 and g = gm/r2. Sun vs moon: the force we feel from the sun is 180x greater than that from the moon, so why does the moon cause the tides, be(cid:272)ause it"s (cid:272)loser.
