## Thursday, May 14, 2009

### Makeup Work

For students who were absent on Monday and missed the video and work, your make up assignment is:

Read through all the lessons on waves and turn in a two page summary.

Students who were absent on Tuesday:
Read through the page, answer any questions that are in the "lecture" part and summarize the content. Turn in the answers and summary next class.

ASSIGNMENTS CAN BE TURNED IN ON THIS SITE!
If you would like, you can do your work in Word, or another text editor, and then cut and paste it into the comments section. Select "Name/URL" for posting the comment, and then enter the names of the people in your group. You do not have to enter anything where it says "URL". I will then review it and grade it online.

1. NikitaCecoyFreddyWagnerMay 14, 2009 at 9:57 AM

Oscillation

1) Why does the length of the acceleration indicator bar fall back to zero after the cannonball leaves the cannon? Because the cannonball doesn’t have an acceleration force anymore.
2) Describe the relationship between force and displacement for the cannonball as it travels along the barrel. Force is independent of displacement
3) How is the graph is consistent with the relationship F = ma? Force is proportional to acceleration..
4) What is the displacement when force is zero? Zero
5) Describe the relationship between force and displacement. Force is proportional to displacement in the opposite direction
6) How does this new oscillation affect the relationship between force and displacement? It doesn’t change
7) What is the displacement when acceleration is zero? Zero
8) What do you notice about the relative directions of force and acceleration? They go in the same direction
9) Describe the relationship between force and acceleration. Force is proportional to acceleration.
10) What is the acceleration when displacement is a) zero, and b) at its maximum value? Zero and at its maximum value
11) What are the relative directions of displacement and acceleration? In the opposite direction
12) What has happened to the gradient of the graph? Increased
13) which is constant while the ball is in the barrel and then falls to zero after the ball has left? The acceleration
14) which increases steadily while the ball is in the barrel? Velocity
15) What are the main differences between the nature of the force on the cannonball and the nature of force that produces oscillation? The force on the cannonball is constant and in the same direction as the displacement. With oscillation it varies with displacement and is in the opposite direction to it, thus acting as a restoring force.
16) are displacement and velocity always in opposite directions? No
17) What is the displacement when velocity has its maximum value? Zero
18) Where is the boxing glove when it exhibits its fastest movement? At equilibrium
19) What do you notice about the value of acceleration when velocity is zero? at its maximum.
20) What is the velocity when displacement has its maximum values? Zero
21) What is acceleration when displacement is zero? Zero
22) Of the variables frequency, period, angle and angular velocity, which are time-dependent and which are constant? Angle is time-dependent while everything else stays the same
23) What do you notice about the values of 2πft angle θ? They are the same.
24) What range of values may sin 2πft have? –1 to +1.
25) What range of values may x have? Between –A and +A.

2. NikitaCecoyFreddyWagnerMay 14, 2009 at 10:09 AM

Wave Behavior

1. Which way are the reflected waves moving? They are moving down and across the original wave.
2. How would you make the ripple tank produce waves of a smaller wavelength? You would have to make the motor move faster to make the waves move more frequently
3. What happens to plane waves after reflection? It turns into a circular wave.
4. What happens to the curved reflected waves? They start to become smaller and focus on to one point.
5. What shape does the reflected wave have? circular
6. Where do the reflected waves seem to come from? They come from a point behind the reflector which is the same distance from the original source of the waves.
7. What happens to the wave? when entering the shallow water the waves start to change direction..
8. What happens to the speed of the waves? The wave speed is slower.
9. What happens to the wavelength? The wavelength is reduced.
10. Which way is the wave moving? left to right.
11. Which way are the particles moving? Up and down.
12. How high is your wave above the center line? 1 cm
13. What is the amplitude now? 7.5 cm
14. What is the distance between two wave tops? 15 cm
15. What is the amplitude of the wave? 5 cm
16. What happens? The wave crests get closer together.
17. What is the wavelength now? 10 cm
18. What is the wavelength now? 20 cm
19. What is the amplitude now? 5 cm
20. Have you changed the energy carried by the wave? the wave amplitude did not change.
21. What is the amplitude of the wave and its wavelength? Its amplitude is 5 cm and its wavelength is 15 cm.
22. What happened to the velocity of the wave? It increased
23. Have they changed? No
24. What happens? the wavelength and velocity remain the same but the height of the crests and the depth of the troughs were changed
25. What happens? the distance between neighboring crests and neighboring troughs were changed but not the amplitude or velocity.
26. Where is the other red particle at that moment? Same height
27. Where is the yellow particle at this moment? At the lowest point
28. Where is the other red particle at this moment? Lowest point
29. Where is the yellow particle at this moment? Highest point
30. How far apart are the two red particles? One wavelength
31. How far apart are the red and yellow particles? Half a wavelength
32. Which ones get through both the circular filter? The vertical ones
33. what happens to the vertical waves now? They cannot pass the filter
34. what happens to the horizontal waves now? They get through the first but not the second
35. how could you allow the horizontal waves to get throught the second filiter? rotating it 90 degrees
36. How far did the wave travel? 24 m
37. What is the connection between the numbers in each row of the table? v= fw
38. Which way is the wave moving? left to right.
39. Look at the particles in the material. How is their disturbance different to the way they are disturbed by a transverse wave? the particles are moved from left to right, rather than up and down.
40. Assuming the background lines are 1 cm apart, what is the maximum displacement of a particle from the middle of its motion? 0.5 cm
41. What is the amplitude now? About 0.25 cm.
42. How did you do this? increasing the amplitude.
43. Assuming the vertical background lines are 1 cm apart, what is the distance between the centres of two neighbouring compressions? Approximately 10 cm.
44. Approximately 10 cm. Approximately 10 cm.
45. How does this compare to the distance between compressions? the same.
46. What is the wavelength now? About 13 cm.
47. What is the amplitude of the wave? 0.5 cm
48. What is the wavelength of the wave? 10 cm
49. What has happened to the velocity of the wave? Increased.
50. What is the amplitude of the wave now? 0.5 cm
51. What is the wavelength of the wave now? 10 cm
52. What do you notice about the amplitude and wavelength of the wave as the velocity changes? stays the same.
53. Using this information, why do you think you see a lightning flash before hearing thunder? Light travels faster than sound.
54. find the minimum wavelength value. 5 cm
55. What is the maximum wavelength value? 20 cm
56. How do they move? Back and forth either side of their rest position.
57. As a result of the passage of the wave, how have the layers either side of this one been moved from their rest position on one of the vertical lines? moved closer to this layer.
58. As a result of the passage of the wave, how have the layers either side of this one been moved from their rest position on one of the vertical lines? moved farther from this layer.
59. From the graph, what is the approximate displacement of the green layers at the middle of a compression? Zero
60. From the graph, what is the approximate displacement of the red layers at the middle of a rarefaction? Zero
61. When the displacement graph is positive, which way have the particles been displaced from their rest positions? To the right.
62. When the displacement graph is negative, which way have the particles been displaced from their rest positions? To the left.
63. How does this affect the air pressure? reduces it.
64. What is the height in divisions of the crest of the wave on the screen? Two divisions.
65. What is the amplitude of the wave, in volts? 2 × 0.2 = 0.4 V
66. What is the wavelength, in divisions, of the wave on the screen? Four divisions.
67. What time is represented by the wavelength value? 4 × 0.5 = 2 ms = 2/1000 in seconds
68. Use this equation to calculate the frequency of the sound you see being displayed on the oscilloscope screen. 1000/2 = 500 Hz
69. What is the periodic time and the frequency of this sound? About 12 ms and 80 Hz.

3. NikitaCecoyFreddyWagnerMay 14, 2009 at 10:26 AM

Combining Waves

How do their amplitudes and wavelengths compare? same.

Are the waves in phase or out of phase with each other? In phase.

How do these two waves compare in amplitude and wavelength? the same.

Are they in phase or out of phase with each other? They are out of phase.

Predict what will happen when the two waves are added. They cancel out.
How do the two waves compare in amplitude? The amplitude of the blue wave is one third of the amplitude of the red wave.
How do they compare in wavelength? The wavelength of the blue wave is one third of the wavelength of the red wave.
How do they compare in frequency? The frequency of the blue wave is three times the frequency of the red wave.
How far apart are the nodes or antinodes in terms of red or blue wavelengths? Half of a wavelength.
When the red and blue waves are in phase are they added constructively or destructively? Constructively
When the red and blue waves are out of phase are they added constructively or destructively? Destructively
How many times does this resonance happen? 4
What are these frequencies? 15, 30, 45, and 60 units.
How many antinodes are seen at each of these frequencies? One, two, three, and four antinodes, respectively.
What is the ratio of the frequencies that cause resonance? 1:3:5
What is the ratio of these frequencies to the lowest frequency found in the closed tube? 1:2:4
So, from the length of your first resonant position, what is the wavelength of the sound you have heard? 4 × 0.215 = 0.860 m
From this equation and your wavelength value, what is the velocity of the sound in the air of the tube for this frequency of tuning fork? 384 × 0.860 = 330 m s–1
How does this length compare with the first one? Its 3 times as long.
Repeat the experiment and see how many resonant positions you can find. How many are there? 3
From the length of the second one, where there are three node-antinode distances, what is the wavelength and velocity of the sound? 0.688 m and 330 m s–1.
What happens to the wave? Spreads around two obstacles
What difference do you see in the waves that diffract through the narrow gap? The waves are diffracted through a wider angle when they pass through a narrow gap.
What do you notice about the area to the right of the barrier compared to the single-slit picture? The wave crests is missing in two regions.
What would you expect to happen where two wave crests meet? A high crest would be formed
What would you expect to happen where two wave troughs meet? A low trough would be formed
Now look for places where a crest from one wave source meets a trough from the other. What would you expect to happen in these places? The water is calm cause the crest of one wave is cancelled out by the trough of the other one
What happens at the point marked with a red dot? The wave crest from source 1 meets the wave crest from source 2 and makes a higher crest
What is the difference between your two answers in terms of wavelengths? Zero wavelengths.
How do these differ from the other cases? They are both cancellations, where a crest from one source meets a trough from the other.
What do these straight lines represent? Regions of cancellation where crests from one source meet troughs from the other.
What does this do to x? Increasing the source separation a decreases x.
What does this do to x? Increasing the wavelength increases x.
What does this do to x? Increasing the distance to the cross-section increases x.