Getting down to business''

1
Lecture 11

• Getting down to business..

2
Last Time

• We covered the topic of Energy
• Bolemon Chapter 6
• Problems to try pg 123 1,2,3 (use energy),
  5,9,15,16
• Energy is conserved.
• The energy when a process starts is the same as
  the total energy at the end but it could change
  into various forms.
• Springs have potential energy ((1/2)kx2 when they
  are extended or compressed.
• We demonstrated that the string on a guitar
  behaves like a spring.

3
During Oscillation (Important for Music)
4
Conclusions

• The bigger the mass the lower the frequency.
• The bigger the spring constant (stiffer) the
  higher frequency.

5
The Tones
f0
6
OCTAVE
7
The Strings
8
FRETS
9
Take a close look at what the string is actually
doing STANDING WAVES
NODE
NODE
10
A Flash Photograph
NODE
11
What is a node???

• A point where nothing changes with time.
• The fixed end of the string is a node
• There are associated nodes with standing waves.

12
A Closer Look
ROCKING POINT
FIXED BY HARDWARE
13
How does the thing work?STANDING WAVES

• What is standing?
• What is a wave?

14
DEMO -01

• Lets do the wave.

15
Demo -02

• The rope to the back of the room.

16
What was traveling along the rope??

• The rope didnt go anywhere.
• Segments of the rope moved up and down.
• This up and down motion means that each little
  piece of the rope has kinetic energy.

17
The pulse moves with a speed v.
18
Another look at the pulse
Rope not moving anywhere
Rope not moving anywhere
Rope not moving anywhere
Rope not moving anywhere
Rope not moving anywhere
Rope not moving anywhere
19
Closer Look
Lots of Kinetic Energy Here
20
Time goes by
It's the ENERGY that moves!
Energy
Energy
21
What happens at the other end?
22
Not fixed at the end???
23
Guitar String CONSTRAINTS

• The string is tight.
• The two ends are FIXED.
• They are always NODES.

24
Harmonic Wave
25
Harmonic Wave
26
Harmonic Wave
T
27
Adding Waves
http//www.schulphysik.de/suren/Applets.html
28
The String