Physics 2211: Lecture 33

1
Physics 2211 Lecture 33
Conservation of Energy Kinetic
Energy Gravitational Potential Energy
2
Energy

• One of the most important concepts in physics
• No single definition applies to all
  situations.
• Not clearly identified until the middle of the
  19th century.

3
Types of Energy

• Kinetic Energy K energy of motion (readily
  available)
• Potential Energy U energy of forces (stored
  energy)
• Chemical Energy
• Heat
• Nuclear Energy

4
Energy during Free Fall
Generalization Chalk Time Additional Notes
(Important)
5
Fact of Nature Conservation of Total Energy
KU is fixed. But we can convert K into U or U
into K as often as we like.
An analogy might help . . .
6
Conservation of Total Energy
7
Which statement is true?
8
The choice of y 0 is arbitrary so reasonable
people can disagree about the value of the
potential energy. It can even be negative!
Therefore, the value of E U K is arbitrary
also.
9
(No Transcript)
10
Potential Energy due to Gravity
zero is fixed at infinity!
11
Escape Velocity
12
(No Transcript)
13
Amazing Fact of Nature
All the gravitational potential energy in the
Universe is negative
Add to this all the other types of energy in the
Universe
As far as we can tell, the total energy of the
Universe is zero!
14
Recap
Conservation of Energy Kinetic
Energy Gravitational Potential Energy
Next Lecture
Work-Energy Theorem