# E&S: Lecture 1

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1. What is energy?
• -scalar quanity, related to the energy content of a system, no direction
• -movement
• -capable of accomplishing work
• -conserved
• -SI system: Joules (J)
2. Force
• -Act at a distance and cause bodies to accelerate
• -Units: kg m sec^-2
• F =ma
3. 4 forces
• 1. Gravitational
• 2. Electromagnetic
• 3. Strong nuclear
• 4. Weak nuclear
4. Work
• -Force integrated over distance
• -lifting things, smashing things takes work
• -Units: Joules (J)
• W=Fd
5. Kinetic energy
• -energy associated with moving objects
• KE= 1/2mv^2
6. Photon energy
• -Massless bundles of electromagnetic energy
• -Electromagnetic radiation cam be described as electromagnetic waves or particles
7. Equation: Energy of photons
E=hf
8. Heat energy
- kinetic energy associated with the random motions of atoms and molecules
9. why can potential energy be stored within systems?
Their physical configuration
10. How can you increase the potential energy of a system?
By doing work againts a conservative force field
11. Potential energy is ______not _____
Potential energy is relative, not absolute
12. Potential energy can be converted to ______
• other forms of energy
• ex. kinetic energy and heat
13. Alteration: Gravitational Potential Energy
Altered by doing work against a gravitational field
14. Alteration: Elastic Potential Energy
Altered by doing work against an elastic material
15. Alteration: Electrostatic Potential Energy
Altered by doing work against an electrostatic field
16. Alteration: Magnetic Potential Energy
Atered by doing work against a magnetic field
17. Alteration: Chemical Potential Energy
Altered by forming and breaking chemical bonds
18. Friction
non-conservative force that resists motion
19. Work done gaints frictional forces
• -does not store potentiale energy
• -dissipated as heat
20. Power
• -A scalar quantity related to the rate of energy gain/loss of a system per unit of time
• Unit: Joules/sec=Watts(W)
21. Humankind's total use of power in 2005
1.1x10^4 GW
22. Firt Law of Thermodynamics
-The change in total internal energy is the sum of heat energy entering the system from its environment plus the work done the system by its environment

• Δ U = Δ Q + Δ W
• Δ U= Internal Energy
• Δ W= Work done
23. Entropy
Measure of a system's unvailability to do work on its environment
24. Entropy: The more orderd the system
the lowery its entropy
25. Entropy: The more disordered the system
The higher its entropy
26. The entropy of the universe as a whole
continously increasing
27. The entropy of a closed system
Never decreases
28. How can the entropy of open systems decrease?
• Only through the application of work