lecture 18 - physics and astronomyphysics.unm.edu/courses/fields/phys160/lecture15.pdf ·...
Post on 01-Apr-2020
1 Views
Preview:
TRANSCRIPT
Lecture 18(Conservation of Energy)
Physics 160-01 Fall 2013
Douglas Fields
Conservation of Mechanical Energy
• The work-energy theorem can be written as:
• And if there are no “other” forces doing work, then:
Other Gravity ElasticW KE U U
0
0
Gravity Elastic
Gravity Elastic
KE U U
E
E KE U U
Problem 7.9
Problem 7.24
k=1.06x104N/m
Problem 7.46
Problem 7.54
Problem 7.75
Forces from Potential Energy
• Since the potential energy is derived from the work as:
• Then, we can relate the Force to the derivatives of the potential energy function:
final final final
initial initial initial
x y zfinal
x y z
initial x y z
U W F ds F dx F dy F dz
, , , , , ,; ;x y z
U x y z U x y z U x y zF F F
x y z
“Topological Map” circa 2009
35°10'49.43" N 106°28'09.65" W
Energy Graphs
• One can learn a lot about the behavior of an object, just by looking at a graph of its potential and total mechanical energies.
top related