Transcript 1.2 - Simple Physics Concepts

2007 - Week 1.2
Some Fundamental Items from
PHYSICS
Assignment

Begin reading the Background
Notes that are posted on the
website.
Roughly pages 1-18
From Our Discussion

Elements of Music






Structured/Designed Sound
 Some pleasant – bells, most musical instruments
 Some nasty – whip
 Some intermediate - drums
Rhythm (time)
Tones (Not defined, though)
Loudness
Pleasurable ????
Message ???? Must there be one? What Kind?
Bone Flute – Music is older
than I am!
50,000 years or more
Neanderthal
reconstructions
Where did instruments come
from???
What does this mean?
Lightening

Takes time to get to you or you are in big
trouble.



Speed = distance/time
What is distance?
What is time?
Sound --- A “disturbance”
Important Definitions

Length or Distance


How “far” something moves or travels.
Measured against some agreed upon standard.
Length Standard .. The Gorf
1
2
Unknown Length = 4
3
1/8 Gorfs
4
1/8
The real standard:
Systems of Units


SI Units …. Meters, Seconds,
Newtons/Kilograms
English System ….. Feet/yards,
seconds, pounds/poundals
More Important Definitions

TIME

The subjective “distance” between two EVENTS.


Original Clock – The Earth’s Rotation


It needs to be objective … ie measurable and
reproducible.
“It is two days journey”
Today’s Clocks –

“He ran the race in 4 hours, 2 minutes and 21.85
seconds”
Things that “tick” at some rate



The planet … once a day
The Pendulum .. Depends on a number of
things;
Parameters:
Mounting
Length
Weight,
whatever
that is.
In case you care…..
Length (L)
period  2
acceleration of gravity (g)
  3.1415926
g  32 ft / s 2
We will discuss this “g-thing” when we
get to acceleration.
Sun Clock
Water Clocks
And so on …
Rolex (~$10K)
Atomic Clock (NASA) $ megabucks
The music clock:
the Metronome
112 quarter notes per minute.
We hear music (and other
noise) in our brains.
Sound
And you didn’t even know that
you have one!
Sound Waves push against
your
Tympanic Membrane
What is a wave, what is a push??
Inside your head
D
d
To Brain
In order to understand
musical tones and their
relationship to each
other, we need to
understand
GRAPHS!
A graph … what does it all
mean?
distance (meters)
100
snail
50
rabbit
1
time (seconds)
2
Speed
distance traveled
Speed 
time it takes to travel that distance
distance (meters)
So….
100
Snail goes 100 meters in
2 seconds …
snail
50
rabbit
Speed=100m/2s
Speed = 2 meters/second
1
time (seconds)
2
Notice
distance
if speed 
,
time
then
distance  speed x time
d  sp
Also



Velocity is speed in a particular direction.
Velocity: 120 m/hr NORTH
Speed: 120 m/hr (or mph)
Example


Sound travels about 1100 ft per second.
How much time does it take for sound to
travel about 1 mile?
d  vt
t  d / v  5280 / 1100 ~ 5 sec
Another Graph .. a biggy!
1.5
disturbance
1
0.5
0
0
5
10
15
-0.5
-1
-1.5
Time (seconds)
20
25
Important Definitions
The PERIOD, T is the time it takes to go from one condition to the next time
that exact condition is repeated.
The frequency, the number of oscillations per second, is given by:
1
frequency 
period
or
1
f 
T
disturbance
1.5
1
0.5
0
0
-0.5
5
10
15
20
-1
-1.5
Time (seconds)
6 sec
25
Period = 6 seconds
Frequency=1/6 per sec (Hz)
=0.16 sec = 160 ms
Siren … a scientific instrument
The Graph
1.2
"airspeed" - relative
1
0.8
0.6
0.4
0.2
0
-0.2
0
2
4
6
8
Time in milli-seconds
10
12
100 Bottles of beer on the wall
…
Loudness
Resonance (later)
Rotational
Speed
(Turns/second)
Helmholtz Resonators
Helmholtz’s Results
Note from Middle C
C
D
E
F
G
A
B
Frequency
264
297
330
352
396
440
496