|
1. What is being transfered through a wave?
What isn't being transfered?
Explain why a pulse that is reflected at a rigid point inverts.
Suppose an up pulse travels down towards the fixed end. What happens to the pulse if the fixed end is not rigid? Draw the before and after picture of an up pulse below.
2. State the Principle of Superposition:
If two pulses add up to be a larger pulse, what kind of interference is that?
If two pulses subtract to be a smaller pulse, what kind of interference is that?
3. Define a periodic wave:
What are the two classifications of periodic waves?
Why is a wave at a ballpark considered a transverse wave?
Label the parts of the wave pictured below:
Explain the similarities and differences between a transverse wave and a longitudinal wave. (You should have at least two similarities and at least two differences).
4. Define frequency:
Define Period:
What relationship does period have with frequency: straight line, inverse, inverse square, direct square?
If four water waves pass a buoy every second, what is the frequency?
What is the period?
If the frequency doubles, how many water waves would pass the buoy every second?
How long would it take one water wave to pass the buoy?
5. If a boat sinks and raises back to its original height every 3 seconds, and the crests of the waves are 20 meters apart, find the wave’s frequency, period, and velocity. (f = 1/3 Hz; t = 3 s; v = 6.67 nm/
Find the speed of the individual molecules of water from the water wave if the boat rises and falls 100 cm. (1.05 m/s)
Show that the ratio between the speed of the wave and the speed of the molecule equals:
What relationship does that ratio have with lambda?
What relationship does that ratio have with the radius of the water molecule's circle?
If the amplitude of the wave stays the same (thus r stays constant), what happens to the ratio if the wavelength of the water wave doubles? In other words, how much faster is the wave traveling compared to the molecules? Show why mathematically.
If the wavelength stays the same, what happens to the ratio if the amplitude of the wave doubles (thus r doubles as well)? In other words, how much does the speed of the wave change compared to the speed of the molecules? Show why mathematically.
What happens if both the wavelength and amplitude of the wave triples? Show why.
6. Find the wavelength and frequency for each standing wave below. Why can n, the number of nodes, only be whole numbers and not fractions with standing wave?
A stretched wire 2.00 m long has a fundamental frequency of 400 Hz. What is the speed of the waves in the wire? (v = 1600 m/s)
A stretched wire 5 m long has a standing wave with a speed of 1000 m/s. What is its fundamental frequency? (100 Hz)
For the previous problem, what would be the second and third overtone for that particular standing wave? (200 Hz and 300 Hz)
7. What type of wave is sound: transverse or longitudinal?
Draw how the air molecules vibrate from a source and label the parts of the wave:
What do compressions coincide with on a transverse wave?
What do rarefactions coincide with on a transverse wave?
8. Rank the following mediums from fasted to slowest for sound: liquid, solid, gas.
Explain why sound travels faster in a solid compared to a gas.
Explain why sound travels faster in hot temperatures compared to colder temperatures.
How are hot temperature molecules different from molecules in a solid?
Why do you suppose they both produce the fastest sound?
9. A person at a baseball game is sitting 1000 feet from the batter (nosebleed seats). How long does it take to hear the crack of the bat after you see it happen? (.89 s)
A person hears the starting gun in a race 1.5 seconds after he sees the smoke. How far away from the gun is he? (515 m)
A person sitting 350 meters from the starting gun hears it .98 seconds after it goes off. Is it hotter or colder than usual for that day? Show why mathematicall.
Often time people will put their ear to a railroad track to see if they hear the train coming because they will hear it through the steel rail before they will in the air. If the train is 2.0 km away (2000 meters), and it blows its whistle, how long will it take the sound to reach the person's ear on the rail? (t = .40 s)
How long will it take the sound to reach the person listening in the air? (t = 5.8 s)
A person takes off in a race car at 250 m/s from the starting line. You are standing at the starting line and you want the person to hear your gun go off when the car hits the 1000 meter mark, so that he can stop. How long after the person takes off should you wait to shoot the gun? (t = 1.1 s)
10. What quantity does the pitch of a sound represent?
What is the distance between the compressions in the air of the sound wave that has the musical pitch C which is 256 Hz? (1.34 meters)
What happens to the wavelength of a sound wave as its pitch increases?
What happens to the frequency of a sound wave if the wavelength is increased?
What happens to the frequency of a sound wave if it is made louder? Explain.
What relationship does wavelength have with frequency: direct straight line, direct square, or inverse? Answer and show by the equation.
If the pitch is doubled, how does the wavelength change?
If the pitch is cut by one third, how does the wavelength change?
Sub-woofers in a car are for the base in the music. Are the wavelengths eminated from those speakers longer or shorter than those coming from the tweeders (high pitches)?
11. Draw the diagram of the ear and label each important part.
Explain the process of how someone hears from the time the sound wave enters the outer ear canal (auditory meatus).
Why do people lose the ability to hear high pitches before the low pitches?
Why can dogs hear high pitches (frequencies) than humans?
12. A 10,000 Hz train whistle is blowing while the train is moving at 50 m/s towards a listener who is at rest. Find the frequency the listener hears. (11,500 Hz)
The train is now at rest, and the listener is moving towards the whistle at 60 m/s. Find the frequency the listener hears. (
The train is now moving away from the listener at 50 m/s, and the listener is at rest. Find the frequency the listener hears.
Both the train and the listener are moving away from one another at 50 m/s. Find the frequency the listener hears. (7,450 Hz)
You are riding in a car towards siren that is at rest with a frequency of 5,000 Hz. How fast are you going if you hear the siren with a frequency of 6,000 Hz? (68.6 m/s).
Show that you can write the velocity of the listener as:
 When the source is at rest, and V represents the speed of sound.
13. Explain a sonic boom and mach speed:
Does a sonic boom occur every time a plane flies overhead, or just once?
Use the diagram below and derive the equation for the angle of the shock wave:
In the picture above, label the low pressure and high pressure zones.
If an airplane is traveling at Mach 2, find the angle of the shock wave. (Theta = 30 degrees)
If the angle of the shock wave is 45 degress, find how fast the airplane is moving. (485 m/s)
What mach speed is that? (mach 1.4)
What happens to the angle of the shock wave as the speed of the object increases?
14. An airplane is traveling at 446 m/s. Find the angle of the shock cone. (50 degrees).
How long will it take the sound to reach your ears after the plane passes directly overhead?
List the following in order: A person feels the sonic boom, a person sees the plane, a person hears the plane.
15. If the length of a guitar string is cut in half, what happens to its pitch? Explain. (doubles)
If the tension in the string is increased nine times, what happens to the pitch? Explain. (increases by three)
If the linear density is decreased by nine times, what happens to the pitch? Explain. (increases by three)
If the length of the guitar string is cut in third while the tension is increased by four and the linear density is increased by a factor of 16, what happens to the pitch? (increases 1.5 times)
16. Every object has a frequency, which causes the object to vibrate when that frequency is matched by something else.
Explain why the bumper of a car only rattles at certain speeds.
Give an example of resonance that you have experienced in your life.
17. How do wind instruments create sound?
What two things does the pitch depend on?
How is that similar to the pitch of a stretched string?
How is it different?
Draw in the standing waves for the given tubes:
 For the fundamental frequency, the tube is 14-cm. What is the wavelength of the standing wave? (56-cm)
For the first overtone, the tube is 12-cm long, what is the wavelength of the standing wave? (16-cm)
For the third overtone, the wavelength is 4-m, what is the length of the tube?
You have a tuning fork with a frequency of 256 Hz. How long of a tube do you need in order to create a standing wave? Assume the tube is closed on one end. (33-cm)
As the temperature of the air gets hotter, will you need longer tubes or shorter tubes to create the standing waves? Explain.
18. Draw in the standing waves for the given tubes:
 The length of the first tube is 10-cm, what is the wavelength of the standing wave? (20 meters)
Come up with an equation for wavelength based on the number of nodes present in the tube (Like we did in class for standing waves).
You have a tuning fork with a frequency of 480 Hz. How long of a tube do you need in order to create a standing wave? Assume the tube is open on both ends. (36-cm)
If your tube length is .50 meters long, what frequency of sound will you need to set up the first overtone? (686 Hz)
|
