Transcript 1CT_Sp07_intro_sound..>

• Have you ever taken a physics
course before?
• Do you play an instrument?
• Can you read music?
Why are you taking this class?
Do you have an Iclicker?
A) Yes, I do!
B) Not yet…
(Please register it, see our web page)
CT 1.0.2
To do well in this class, how many
hrs/week do you expect to spend
outside of lecture?
a) < 2 hrs each week
b) 2-4 hrs
c) 4-6 hrs
d) 6-8 hrs
e) 8+ hrs
CT 1.0.1
How do you think you will learn
physics the best?
a) Listening to lecture
b) Reading the textbook
c) Doing the homework
d) Discussing with others
e) Other…
CT 1.1.1
If a tree falls down in some remote
forest does it make a sound?
a) Yes
b) No
c) Maybe
d) I don’t really understand what this
question is trying to ask!?
CT 1.1.2
The following sound would be classified as:
a)
b)
c)
d)
e)
Musical
Speech
Noise
Organized sound
Transient
CT 1.2.2
If I whack a ruler hanging off the desk, I can
make a “note”.
What happens if I move it back so less
hangs off the edge, but I whack it just as
hard?
A) Pitch , loudness similar
B) Pitch similar, loudness
C) Pitch , loudness
D) Pitch , loudness similar
E) Something else
WHY?
CT 1.2.3
What determines pitch?
Which is the most important feature of the
instrument/source of sound?
A) Length/size
B) “Bendability”/rigidity
C) Heaviness/density of material
D) Amplitude (how hard it is struck)
E) More than one of the above
A-B: very (equally) important
C: Depends!
D is a special case… but usually
does NOT matter (much).
CT1.2.4
Let’s fill the Tibetan singing bowl with
water. What happens to the pitch of
the tone it makes?
A)
B)
C)
D)
goes up
goes down
pretty much unchanged
no way to know this without
trying
Why?
CT 1.4.7
Speed of sound
Which sounds travel the fastest through air?
a)
b)
c)
d)
e)
Higher pitch
Lower pitch
Louder sounds
Quieter sounds
They all travel at the same speed
And a darn good thing…
(344 m/s in room temperature air.)
CT 1.4.1
Approximately how close is a thunderstorm
if you see lightning flash and hear a clash of
thunder after counting up to 6 seconds?
(the speed of sound is 344 m/s)
a) 0 km
b) 1 km
c) 2 km
d) 6 km
e) None of these
CT 1.4.2
You are traveling on a commercial airplane (say
a Boeing 757). Relative to the speed of sound
you are traveling:
a)
b)
c)
d)
e)
much slower than sound
a little slower than sound
the same speed as sound
a little faster thaqn sound
much faster than sound
CT 1.4.4
In which of the following venues can you notice
a difference between the music you perceive
and the movements of the musicians (i.e. can
you tell that the sound has traveled a distance?)
a)
b)
c)
d)
The rear of the Fox Theater
Pepsi Center
Red Rocks amphitheater
All of the above
Textbook says about 20 meters (about 60
feet, about the width of the grass field in the
stadium) is where most people start to
notice «lag».
CT 1.4.5
In a 32 o C room sound travels…
a) > 344 m/s
b) 344 m/s
c) < 344 m/s
Speed depends on the temperature
Depends on the medium
(Faster through solid metal than
through air, e.g!)
What if the room is 32o F? Does the sound
travel faster or slower than a 32o C room?
a) Faster
b) Slower
c) Same speed
Do you need to know temperature
if you want to directly measure the
speed of sound (by measuring
distance traveled and time taken)?
A) Yes
B) No
CT 1.4.6
When sound travels from a source to a listener,
what do air molecules never do?
a)
b)
c)
d)
e)
Travel from the source to the listener at
344 m/s
Move back and forth with the frequency of
the sound wave
Bump into other air molecules
Move in the direction of wave propagation
Air molecules do all of the above
CT 1.4.3
Sound travels at a speed of 344 m/s (770 mph).
How fast does the air flow out of my mouth as I
speak?
a)
b)
c)
Much slower than 344 m/s
344 m/s
Much faster than 344 m/s
CT 1.5.2
I stand on a scale with both feet and
measure my weight. If I stand on one foot,
does the reading:
a) Increase
b) Decrease
c) Remain the same
d) ???
When I stand on one foot, does the
pressure on the other foot (the one
that remains on the ground)…
a) Increase
b) Decrease
c) Remains the same
d)??
CTR1.3
You’re clapping in front of a wall, a distance
“D” away from you. The pattern is
clap-pause-echo-pause-clap-pause-echo…
(evenly spaced… picture it!)
Your friend times your claps (not the echos!)
and counts 6 claps in 10 seconds.
What’s the speed of sound?
A) 4 D / (0.6 sec)
B) 2 D / (0.6 sec)
C) D / (0.6 sec)
D) 10 D / (.6 sec)
E) D / (1.2 sec)
How fast (frequently) can you tap
the desk?
(What’s your clapping frequency
in Hz?)
CT 2.1.3
If I lower the frequency of this tone what
happens to the pitch?
a)
b)
c)
d)
It decreases
It increases
It remains the same
Not enough information
What if I make the same sound louder
(keeping the same pitch),
the frequency…
CT 1.5.1
If there is really a force of 105 N (that’s
100,000 N, about 11 tons!) on each square
meter of a glass window, why is it that the
window does not shatter?
a) That is such a small force it does not matter
b) Other forces (e.g. from the frame) counteract
and balance this
c) Glass is stronger than you think
d) There is an equal but opposite force of air
pushing against the window from the other side
e) Gravity counteracts the force
CT 1.5.3alt
a) I weigh 500 N, what is the force
on each foot?
a)
b)
c)
500 N each
250 N each
It depends on the area of my foot
CT 1.5.4
Who is more likely to damage a hardwood
dance floor, while just standing around?
a)
b)
c)
d)
A 250 lb person wearing boots with 2 cm x
2 cm heels
A 100 lb person wearing 1 cm x 1 cm heels
They will do equal damage
Not enough information to make an
informed choice
(Pressure = Force/ area)