[PHYS 121] - Final Exam Guide - Ultimate 141 pages long Study Guide!
Document Summary
To facilitate our accounting of energy in the rest of the book, we divide all energy into four categories: kinetic energy, k, potential energy, u, source energy, e(s, thermal energy, e(th) Interactions convert energy from one category to another, but conservation of energy requires that, for a closed system, the energy e of the system remains unchanged. Examples of reversible conversions: conversion between gravitational potential energy and kinetic energy for a ball thrown vertically upward, conversion between elastic potential energy and kinetic energy for a cart hitting a spring. The generation of mechanical energy from source energy is always accompanied by the generation of thermal energy. Because of dissipation, all forms of energy are eventually converted to thermal energy. Our ability to recover mechanical energy from thermal energy is very limited, making thermal energy not as useful as other forms of energy.
