ASTRON 1101 Lecture Notes - Lecture 17: Chemical Energy, Gravitational Energy, James Prescott Joule
5 Oct 2016
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Document Summary
How long will the sun shine: energy can"t be created or destroyed; it can only change form, chemical potential energy and gravitational potential energy are inadequate to keep the. Sun shining: nuclear fusion of hydrogen into helium keeps the sun shining for ~10 billion years in total. Stars: balls of gas that shine because they are hot. The luminosity of a star is the rate at which it loses energy (in the form of photons that are thrown away into space) The sun loses joules of energy per second: equivalently, the luminosity of the sun is watts. Unit of force = 1 newton = about 4 ounces (3. 597 oz. ) Unit of distance = 1 meter = 39 inches (39. 37 in) Unit of work = 1 newton meter = 1 joule. When a quarter-pound apple is lifted 39 inches, 1 joule of work is being done. Short definition of energy: energy is the capacity to do work.
