Midterm 1 Notes

Chapter 1 * * Energy is the ability to do work * It can be measured in food Calories, kilowatt-hours and joules * Gasoline has about 10 Cal per gram * Cookies have about 5 * TNT has about 0.65 * Expensive batteries about 0.1 Cal * Fuel cells produce electricity like batteries but are recharged by adding chemicals * Uranium has 20 million Calories per gram * Power is the rate of energy delivery and can be measured in Cal/sec or in watts * 1 hp = 1 kW * Large nuclear plants can create electricity with a power of about 1 GW * Kinetic energy is the energy of motion * To have the same energy as TNT, a rock has to move at about 1.5 miles per second * The rock that hit the earth was moving about 15 miles per second (100x energy of TNT)
Chapter 2 * Atoms are about 10-8 cm in diameter * There are about 50,000 of them in the diameter of a red blood cell * Heat is the shaking of molecules * The velocity of shaking is comparable to the velocity of sound (1000 feet per second) * If two objects have the same temperature, then the average kinetic energy of the molecules in the two objects is the same * However, the speed of the molecules is not equal. * If two molecules with different masses have the same kinetic energy, the lighter molecule will have higher velocity * Laws of thermodynamics * Objects in contact tend to reach the same temperature * Energy is conserved * Extracting useful energy from heat required a temperature difference * The entropy of the Universe is always increasing
Chapter 3 * Weight is the force of gravity acting on mass * The force of gravity obeys an inverse square law * Weightlessness = continuous falling * LEO = 8km/s and orbits Earth in 1.5h * Geosynchronous satellites orbit around the equator (24h) * MEO GPS * Satellites must fly high (200km+) to avoid air resistance * Acceleration can also be