# Midterm 1 Notes

Topics: Energy, Nuclear fission, Entropy Pages: 3 (788 words) Published: December 11, 2012
Chapter 1
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* 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
* 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 measured in...