Physics 2211: Lecture 36

1
Physics 2211 Lecture 36
Hookes Law Elastic Potential Energy
2
Some Vocabulary
3
If not for elastic forces, there would be no
(living) bungee jumpers . . .
4
(No Transcript)
5
Galloping Gertie -- The Tacoma-Narrows
Bridge
6
(No Transcript)
7
Experimental Fact Hookes Law
8
k 50 N/m
Block slips when spring force on block exceeds
maximum static friction force
9
What force F holds the box at rest if it is
displaced a distance X?
10
(No Transcript)
11
Elastic Potential Energy
since d(se)0
12
Conservation of Energy
Elastic Potential Energy
13
(No Transcript)
14
When the bob hangs vertically and moves in a
circle at constant v, the spring is stretched
from its natural length L by an amount s. Write
the total energy of the system without using the
quantity s.
15
Ls
Must use plus sign to substitute in E
16
A ½ N collar slides 6 cm down a smooth rod. The
unstretched length of the spring (k 30 N/m) is
4 cm. What is the speed of the collar when it
reaches the bottom?
1. 3.2 cm/s
2. 0 cm/s
3. 6.4 cm/s
4. does not reach the bottom
5. 1.8 cm/s
17
(No Transcript)
18
Recap
Hookes Law Elastic Potential Energy
Next Lecture
Knight Section 10.6 Elastic Collisions