Multimedia Science School

- Physics

--- Oscillations and Waves

------ Oscillations - Lesson

------ Wave Behavior - Lesson

------ Combining Waves - Lesson

Go through all three lessons, answering the questions on a sheet of paper. One sheet per group. Make sure ALL group members actually work on it. I will be deducting points for students who are not participating.

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. I will then review it and grade it online.

Slide 3

ReplyDeleteWhich way are the reflected waves moving?

Downwards, across the original wave.

How would you make the ripple tank produce waves of a smaller wavelength?

Make the motor run faster so that the wooden beam vibrates more frequently.

Slide 4

What happens to the plane wave after reflection?

It becomes a circular wave.

What happens to the curved reflected waves?

They get smaller and concentrate into a point.

Slide 5

What shape does the reflected wave have?

A circular shape.

Where do the reflected waves seem to come from?

They seem to come from a point behind the reflector that is the same distance from it as the original source of the waves.

Slide 6

What happens to the wave?

The wave changes direction when it enters the shallow water.

What happens to the speed of the waves?

The wave speed is less in the shallow water.

What happens to the wavelength?

The wavelength is reduced in the shallow water.

Slide 8

Which way is the wave moving?

From left to right.

Which way are the particles moving?

Up and down.

Assuming the background lines are 1 cm apart, how high is your wave above the black centre line?

1 cm

What is the amplitude now?

7.5 cm

Slide 9

Assuming the background lines are approximately 1 cm apart, what is the distance between two wave tops?

15 cm

What is the amplitude of the wave?

5 cm

Move the Wavelength slider to the far left. What happens?

The wave crests get closer together.

What is the wavelength now?

10 cm

What is the wavelength now?

20 cm

What is the amplitude now?

5 cm

Have you changed the energy carried by the wave? Explain your answer

No, because the wave amplitude has not changed.

Slide 10

What is the amplitude of the wave and what is its wavelength?

Its amplitude is 5 cm and its wavelength is 15 cm.

What has happened to the velocity of the wave?

It has increased.

Measure the amplitude of the wave and wavelength again. Have they changed?

No

Slide 12

Move the Amplitude slider back and forth to see its effect on all parts of the wave. What happens?

The amplitude changes the height of the crests and the depth of the troughs, but not the wavelength or velocity.

Move the Wavelength slider back and forth to see its effect on all parts of the wave. What happens?

The wavelength changes the distance between neighboring crests and neighboring troughs, but not the amplitude or velocity.

Slide 13

Where is the other red particle at this moment?

At the same height.

Where is the yellow particle at this moment?

At its lowest point.

Where is the other red particle at this moment?

At its lowest point.

Where is the yellow particle at this moment?

At its highest point.

How far apart are the two red particles?

One wavelength.

How far apart are the red and yellow particles?

Half a wavelength.

Slide 14

Which ones get through both of the circular filters?

The vertical ones.

What happens to the vertical waves now?

They cannot pass through the filter.

What happens to the horizontal waves now?

They get through the first filter but not the second one.

How could you allow the horizontal waves to get through the second filter?

By rotating it 90°.

Slide 15

Look at the length of the wave on the scale. How far did the wave travel?

24 m

What is the connection between the numbers in each row of the table?

Velocity = frequency × wavelength

Slide 17

Which way is the wave moving?

From left to right.

Look at the particles in the material. How is their disturbance different to the way they are disturbed by a transverse wave?

Here the particles are disturbed from left to right, rather than up and down.

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

What is the amplitude now?

About 0.25 cm.

How did you do this?

By increasing the amplitude.

Slide 18

Assuming the vertical background lines are 1 cm apart, what is the distance between the centres of two neighboring compressions? (Particles at the centre of each compression should be on, or close to a vertical line.)

Approximately 10 cm.

What is the distance between the centres of two neighboring rarefactions? (Again, particles at the centre of each rarefaction should be on, or close to a vertical line.)

Approximately 10 cm.

How does this compare to the distance between compressions?

It is the same.

Pause the wave. What is the wavelength now?

About 13 cm.

Slide 19

What is the amplitude of the wave?

0.5 cm

What is the wavelength of the wave?

10 cm

What has happened to the velocity of the wave?

It has increased.

What is the amplitude of the wave now?

0.5 cm

What is the wavelength of the wave now?

10 cm

What do you notice about the amplitude and wavelength of the wave as the velocity changes?

Amplitude and wavelength stay the same.

Why do you think you see a lightning flash before hearing thunder?

Because light travels much faster than sound.

Slide 20

Find the minimum wavelength value.

5 cm

What is the maximum wavelength value?

20 cm

Slide 22

How do they move?

Back and forth either side of their rest position.

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?

They have moved closer to this layer.

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?

They have moved further from this layer.

Slide 23

From the graph, what is the approximate displacement of the green layers at the middle of a compression?

Zero

From the graph, what is the approximate displacement of the red layers at the middle of a rarefaction?

Zero

When the displacement graph is positive, which way have the particles been displaced from their rest positions?

To the right.

When the displacement graph is negative, which way have the particles been displaced from their rest positions?

To the left.

Slide 24

How does this affect the air pressure?

It reduces it.

Slide 25

What is the height in divisions of the crest of the wave on the screen?

Two divisions.

What is the amplitude of the wave, in volts?

2 × 0.2 = 0.4 V

What is the wavelength, in divisions, of the wave on the screen?

Four Divisions

What time is represented by the wavelength value?

4 X 0.5 = 2ms = 2/1000 in seconds

Use this equation to calculate the frequency of the sound you see being displayed on the oscilloscope screen.

1000/2 = 500Hz

What is the periodic time and the frequency of this sound?

About 12 ms and 80 Hz

Lesson3

How do their amplitudes and wavelengths compare?

They are the 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?

They are the same.

Predict what will happen when the two waves are added

They will 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 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?

Four

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?

It is three times as long.

How many resonant positions you can find. How many are there?

Three

What is the wavelength and velocity of the sound?

0.688 m and 330 m s–1.

What happens to the wave?

The wave spreads around the edges of the 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?

There are two regions where the wave crests are missing.

What would you expect to happen where two wave crests meet?

A very high crest would be formed.

What would you expect to happen where two wave troughs meet?

A very low trough would be formed.

What would you expect to happen in these places?

The crest of one wave is cancelled out by the trough of the other one, leaving the water calm.

What happens at the point marked with a red dot?

A wave crest from source 1 has met a crest from source 2 so they reinforce and make a high 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.

Introducing Oscillations

ReplyDelete• The cannonball is no longer experiencing an accelerating force. Acceleration is zero and velocity (neglecting air resistance) is constant

• The force is independent of displacement

• The graph is a straight line that passes through the origin, showing that force is proportional to acceleration. The relationship F=ma applies to all motion of any constant mass, and it shows that the gradient of the graph is the mass m

• When the force is zero, the displacement is also zero

• Force is proportional to displacement, but in the opposite direction

• The relationship is the same as before (but the maximum values of force and displacement are smaller).

• When the acceleration is zero, the displacement is also zero

• The relative directions of force and acceleration are always in the same direction

• Force is proportional to acceleration

• When the displacement is zero, the acceleration is also zero at its maximum value

• The relative directions of acceleration and displacement are always in the opposite direction

• The gradient of the graph has increased

• The acceleration is constant while the ball is in the barrel and velocity increases steadily while the ball is in the barrel

• The force on the cannonball is constant and in the same direction as the displacement. A force producing oscillation varies with displacement and is in the opposite direction to it thus acting as a restoring force

• Displacement and velocity are not always in the opposite directions

• When velocity has its maximum value, displacement is at zero

• The boxing glove is at the equilibrium position when it exhibits its fastest movement

• When velocity is zero, the value of acceleration is at its maximum

• When displacement has its maximum values, the velocity is zero

• When the displacement is zero, the acceleration is also zero

• The values of 2(3.14)ft angle theta are the same

• Sin 2(3.14)ft may have values that ranges from negative 1 to positive 1

• X may have values that ranges from negative A to positive A

Wave Behavior

• The reflected waves are moving downwards, across the original wave.

• To make the rippled tank produce waves of a smaller wavelength you must make the motor run faster so that the wooden beam vibrates more frequently.

• After reflection, the plane wave becomes a circular wave.

• The curved reflections waves get smaller and concentrate into a point.

• The reflection wave has a circular shape.

• The reflected waves seem to come from a point behind the reflector that is the same distance from it as the original source of the waves.

• The wave changes direction when it enters the shallow water.

• Wave speed is less in the shallow water.

• The wave is moving from left to right.

• The particles are moving up and down.

• The wave above the black centre line one cm.

• The distance between two wave tops is 15 cm.

• The amplitude of the wave is 5 cm.

• When you move the wavelength slider to the far left the wave crests get closer together.

• The wavelength is now 10 cm.

• The wavelength is now 20 cm.

• The amplitude is now 5 cm.

• The energy carried by the wave has not changed because the wave amplitude has not changed.

• The amplitude of the wave is 5cm and its wavelength is 15cm.

• The velocity of the wave has increased.

• No, the amplitude of the wave and wavelength did not change.

• The amplitude changes the height of the crest and the depths of the troughs, but not the wavelength or velocity.

• The wavelength changes the distance between neighboring crests and neighboring troughs, but not the amplitude or velocity.

• The other red particle is at the same height.

• The yellow particle is at its lowest point.

• The other red particle is at its lowest point.

• The yellow particle is at its highest point.

• The two red particles are one wavelength apart.

• The red and yellow particles are half a wavelength apart.

• The vertical ones get through both of the circular filters.

• The vertical waves cannot pass through the filter.

• The horizontal waves get through the first filter but not the second one.

• The horizontal waves can get through the second filter by rotating is at 90 degrees.

• The wave travelled 24m.

• The connection between the numbers in each row of the table is velocity = frequency x wavelength.

• The wave is moving from left to right.

• Their disturbance is different to the way they are distributed by a transverse wave because the particles are disturbed from left to right, rather than up and down.

• The maximum displacement of a particle from the middle of its motion is 0.5cm.

• The amplitude is about 0.25cm.

• The amount of energy was increased by increasing the amplitude.

• The distance between the centres of two neighboring compressions is approximately 10cm.

• The distance between the centres of two neighboring rarefactions is approximately 10cm.

• This compares to the distance between compressions because they are the same.

• The wavelength is about 13cm.

• The amplitude of the wave is 0.5cm.

• The wavelength of the wave is 10cm.

• The velocity of the wave has increased.

• The amplitude of the wave is 0.5cm.

• The wavelength of the wave is 10cm.

• As the velocity changes the amplitude and the wavelength stay the same.

• You see lightning flash before hearing thunder because light travels much faster than sound.

• The minimum wavelength value is 5cm.

• The maximum wavelength value is 20cm.

• The vertical layer of air particles move back and forth either side of their rest position.

• They moved closer to this layer.

• They have moved further from this layer.

• The approximate displacement of the green layers at the middle of a compression is zero.

• The approximate displacement of the red layers at the middle of a compression is zero.

• When the displacement graph is positive, the particles displace to the right.

• When the displacement graph is negative, the particles displace to the left.

• When the amplitude slider is set to a lower setting, the air pressure reduces.

• The height of the crest of the wave on the screen is two divisions.

• The amplitude of the wave in volts is 2 x 0.2 = 0.4V

• The wavelength of the wave on the screen is four divisions.

• The time represented by the wavelength value is 4 x 0.5 = 2/1000 in seconds

Niccolai Arenas, Yesenia Llanos, Catalina Estrada, Nataliya Kushta said...

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?

ReplyDeleteYesenia Llanos

Catalina Estrada

Nataliya Kushta

Niccolai Arenas

May 12, 2009

Multimedia Lab

Oscillations

-Why does the length of the acceleration indicator bar fall back to zero after the cannonball leaves the cannon?

Because the cannon ball is not moving anymore.

-Describe the relationship between force and displacement for the cannonball as it travels along the barrel.

The force is independent of the displacement.

-How is the graph is consistent with the relationship F = ma?

The graph is a straight line that passes through the origin, showing that force is proportional to acceleration.

-What is the displacement when force is zero

Zero

-Describe the relationship between force and displacement

The force is proportional to the displacement but they are going in opposite directions.

-How does this new oscillation affect the relationship between force and displacement?

They are the same

-What is the displacement when acceleration is zero?

It is zero

What do you notice about the relative directions of force and acceleration?

They are always in the same direction

-Describe the relationship between force and acceleration.

Force is proportional to the acceleration

-What is the acceleration when displacement is a) zero, and b) at its maximum value?

a. Zero

b. Will also be its maximum value

-What are the relative directions of displacement and acceleration?

Opposite directions

-What has happened to the gradient of the graph?

Increases

-a.) Which is constant while the ball is in the barrel and then falls to zero after the ball has left?

Acceleration

-b) which increases steadily while the ball is in the barrel?

Velocity

-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

-Are displacement and velocity always in opposite directions?

No

-What is the displacement when velocity has its maximum value?

Zero

-Where is the boxing glove when it exhibits its fastest movement?

At the equilibrium position

-What do you notice about the value of acceleration when velocity is zero?

It’s at its maximum

-What is the velocity when displacement has its maximum values?

Zero

-What is acceleration when displacement is zero?

Zero

-Of the variables frequency, period, angle and angular velocity, which are time-dependent and which are constant?

Frequency, period and angular velocity remain constant. And the angle is time-dependent.

-What do you notice about the values of 2πft angle θ?

They are the same

-What range of values may sin 2πft have?

It is between -1 and 1

-What range of values may x have?

Has an interval of .02

-What is the only difference between the motions described by the equation x = A sin 2πft and the equation x = A cos 2πft?

The first equation has an initial displacement of zero and the second has the initial displacement A.

Wave Behavior

-Which way are the reflected waves moving?

It goes downwards

-How would you make the ripple tank produce waves of a smaller wavelength?

Make the motor run faster so that the wooden beam vibrates more frequently.

-What happens to the plane wave after reflection?

It curves

-What happens to the plane wave after reflection?

They get smaller as they get to the center.

-What shape does the reflected wave have?

A circular shape.

- Where do the reflected waves seem to come from?

They seem to come from a point behind the reflector that is the same distance from it as the original source of the waves

-What happens to the wave?

It changes direction when it enters shallow water

- What happens to the speed of the waves?

The wave’s speed is less in the shallow water

-What happens to the wavelength?

The wavelength is reduced in the shallow water

- Which way is the wave moving?

From left to right

- Focus on any particle. Which way are the particles moving?

Up and down

- Assuming the background lines are 1 cm apart, how high is your wave above the black centre line?

1cm

- What is the amplitude now?

7.5 cm

-Assuming the background lines are approximately 1 cm apart, what is the distance between two wave tops?

15 cm

-What is the amplitude of the wave?

5 cm

- Move the Wavelength slider to the far left. What happens?

The wave crest gets close together

- What is the wavelength now?

10 cm

- What is the wavelength now?

20 cm

- What is the amplitude now?

5 cm

- Have you changed the energy carried by the wave? Explain your answer

No, because the wave amplitude does not change

- What is the amplitude of the wave and what is its wavelength?

Its amplitude is 5 cm and its wavelength is 15 cm.

- What has happened to the velocity of the wave?

It has increased

- Click and measure the amplitude of the wave and wavelength again. Have they changed?

No

May 12, 2009 9:02 AM

Pauline Santos, Kevin Ith, Yoshika Wason, Hazel Mabesa said...

1) Why does the length of the acceleration indicator bar fall back to zero after the cannonball leaves the cannon?

The cannonball is no longer experiencing an accelerating force. Acceleration is zero and velocity (neglecting air resistance) is constant.

2) Describe the relationship between force and displacement for the cannonball as it travels along the barrel

The force is independent of displacement

3) How is the graph is consistent with the relationship F = ma?

The graph is a straight line that passes through the origin, showing that force is proportional to acceleration. The relationship F = ma applies to all motion of any constant mass, and it shows that the gradient of the graph is the mass, m.

4) What is the displacement when force is zero?

Zero

5) Describe the relationship between force and displacement

Force is proportional to displacement, but in the opposite direction.

6) How does this new oscillation affect the relationship between force and displacement?

The relationship is the same as before (but the maximum values of force and displacement are smaller).

7) What is the displacement when acceleration is zero?

It is also zero.

8) What do you notice about the relative directions of force and acceleration?

They are always 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?

a) Zero

b) At its maximum value

11) What are the relative directions of displacement and acceleration?

They are always in the opposite direction.

12)What has happened to the gradient of the graph?

It has increased.

13)Of the variables displacement, velocity and acceleration (and ignoring the effects of air resistance):

a) which is constant while the ball is in the barrel and then falls to zero after the ball has left? Acceleration

b) which increases steadily while the ball is in the barrel? Velocity

14) 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. A force producing oscillation varies with displacement and is in the opposite direction to it, thus acting as a restoring force.

15)Looking at the indicator bars, are displacement and velocity always in opposite directions?

No

16)What is the displacement when velocity has its maximum value?

Zero

17) Where is the boxing glove when it exhibits its fastest movement?

At the equilibrium position.

18) What do you notice about the value of acceleration when velocity is zero?

It is at its maximum.

19) What is the velocity when displacement has its maximum values?

Zero

20) What is acceleration when displacement is zero?

Zero

21) Of the variables frequency, period, angle and angular velocity, which are time-dependent and which are constant?

Angle is time-dependent. Frequency, period and angular velocity remain constant.

22) What do you notice about the values of 2πft angle θ?

They are the same.

23) What range of values may sin 2πft have?

Between –1 and +1.

24) What range of values may x have?

Between –A and +A.

25) What is the only difference between the motions described by the equation x = A sin 2πft and the equation x = A cos 2πft?

The first equation has an initial displacement of zero and the second has the initial displacement A.

May 12, 2009 9:50 AM

Jon Terrence Tailane said...

1. The cannonball is no longer experiencing an accelerating force because its slowing down.

2. The force is independent of displacement.

3. The graph is a straight line that passes through zero. F = ma applies to all motion of any constant mass.

4. When force is zero, so is displacement

5. Force is proportional to displacement, but in the opposite direction.

6. The relationship is the same as before but the maximum values of force and displacement are smaller.

7. When acceleration is zero, so is displacement

8. Relative direction of force and acceleration are relatively the same.

9. Force is proportional to acceleration.

10. The relative direction of acceleration and displacement are always opposite

11. The force on the cannonball is constant and in the same direction as the displacement. A force producing oscillation varies with displacement and is in the opposite direction to it, thus acting as a restoring force.

12. Displacement and velocity aren’t always opposite

13. Displacement is zero when velocity is at its maximum value

14. The boxing glove exhibits the fastest speed at its equilibrium

15. Acceleration is at maximum value when velocity is zero

16. Angle is time-dependent. Frequency, period and angular velocity are constant

17. Both values of 2πft and angle θ are the same

18. between -1 & 1

19. Between –A and +A.

20. First equation has an initial displacement of zero and the second has the initial displacement of A.

May 12, 2009 10:01 AM

David, Ngoc, Victoria said...

David Kristy, Ngoc Nguyen, Victoria Nguyen

Why does the length of the acceleration indicator bar fall back to zero after the cannonball leaves the cannon?

The cannonball is no longer experiencing an accelerating force. Acceleration is zero and velocity (neglecting air resistance) is constant.

Describe the relationship between force and displacement for the cannonball as it travels along the barrel.

The force is independent of displacement

How is the graph is consistent with the relationship F = ma?

The graph is a straight line that passes through the origin, showing that force is proportional to acceleration. The relationship F = ma applies to all motion of any constant mass, and it shows that the gradient of the graph is the mass, m.

What is the displacement when force is zero?

Zero

Describe the relationship between force and displacement

Force is proportional to displacement, but in the opposite direction.

How does this new oscillation affect the relationship between force and displacement?

The relationship is the same as before (but the maximum values of force and displacement are smaller).

What is the displacement when acceleration is zero?

It is also zero.

What do you notice about the relative directions of force and acceleration?

They are always in the same direction.

Describe the relationship between force and acceleration

Force is proportional to acceleration.

What is the acceleration when displacement is a) zero, and b) at its maximum value?

a) Zero

b) At its maximum value

What are the relative directions of displacement and acceleration?

They are always in the opposite direction.

What has happened to the gradient of the graph?

It has increased.

Of the variables displacement, velocity and acceleration (and ignoring the effects of air resistance):

which is constant while the ball is in the barrel and then falls to zero after the ball has left?

Acceleration

which increases steadily while the ball is in the barrel?

Velocity

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. A force producing oscillation varies with displacement and is in the opposite direction to it, thus acting as a restoring force.

Looking at the indicator bars, are displacement and velocity always in opposite directions?

No

What is the displacement when velocity has its maximum value?

Zero

May 13, 2009 9:02 AM

Rai'jona Crear, Carlos Velazquez, Cyril Senu said...

Raijona Crear

Carlos Velázquez

Cyril SENU

Oscillations

Why does the length of the acceleration indicator bar fall back to zero after the cannonball leaves the cannon?

The cannonball is no longer experiencing an accelerating force. Acceleration is zero and velocity (neglecting air resistance) is constant.

Describe the relationship between force and displacement for the cannonball as it travels along the barrel.

The force is independent of displacement.

How is the graph consistent with the relationship F = ma?

The graph is a straight line that passes through the origin, showing that force is proportional to acceleration. The relationship F = ma applies to all motion of any constant mass, and it shows that the gradient of the graph is the mass, m.

What is the displacement when force is zero?

Zero.

Describe the relationship between force and displacement.

Force is proportional to displacement, but in the opposite direction.

How does this new oscillation affect the relationship between force and displacement?

The relationship is the same as before (but the maximum values of force and displacement are smaller).

What is the displacement when acceleration is zero?

It is also zero.

What do you notice about the relative directions of force and acceleration?

They are always in the same direction.

Describe the relationship between force and acceleration.

Force is proportional to acceleration.

What is the acceleration when displacement is a) zero, and b) at its maximum value?

A) Zero

B) At its maximum value

What are the relative directions of displacement and acceleration?

They are always in the opposite direction.

A) Which is constant while the ball is in the barrel and then falls to zero after the ball has left? Acceleration

B) Which increases steadily while the ball is in the barrel? Velocity

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. A force producing oscillation varies with displacement and is in the opposite direction to it, thus acting as a restoring force.

Looking at the indicator bars, are displacement and velocity always in opposite directions? NO

What is the displacement when velocity has its maximum value? Zero

Where is the boxing glove when it exhibits its fastest movement?

At the equilibrium position.

What do you notice about the value of acceleration when velocity is zero?

It is at its maximum.

What is the velocity when displacement has its maximum values?

Zero

What is acceleration when displacement is zero?

Zero

Of the variables frequency, period, angle and angular velocity, which are time-dependent and which are constant?

Angle is time-dependent. Frequency, period and angular velocity remain constant.

What do you notice about the values of 2πft angle θ?

They are the same.

What range of values may sin 2πft have?

Between –1 and +1.

What range of values may x have?

Between –A and +A.

What is the only difference between the motions described by the equation x = A sin 2πft and the equation x = A cos 2πft?

The first equation has an initial displacement of zero and the second has the initial displacement A.

Which way are the reflected waves moving?

Downwards, across the original wave.

How would you make the ripple tank produce waves of a smaller wavelength?

Make the motor run faster so that the wooden beam vibrates more frequently.

What happens to the plane wave after reflection?

It becomes a circular wave.

What happens to the curved reflected waves?

They get smaller and concentrate into a point.

What shape does the reflected wave have?

A circular shape.

Where do the reflected waves seem to come from?

They seem to come from a point behind the reflector that is the same distance from it as the original source of the waves.

What happens to the wave?

The wave changes direction when it enters the shallow water.

What happens to the speed of the waves?

The wave speed is less in the shallow water.

What happens to the wavelength?

The wavelength is reduced in the shallow water.

Which way is the wave moving?

It is moving from left to right.

Which way are the particles moving?

Up and down.

How high is your wave above the center black line?

One cm.

What is the amplitude now?

7.5 cm

What is the distance between two wave tops?

15 cm.

What is the amplitude of the wave?

5 cm.

What happens when you move the wavelength slider to the left ?

The wave crests get closer together

What is the wavelength now?

10 cm.

What is the wavelength now?

20 cm

What is the amplitude now?

5cm

Have you changed the energy carried by the wave?

No, because the wave amplitude has not changed.

What is the amplitude of the wave and what is its wavelength?

Its amplitude is 5 cm and its wavelength is 15 cm.

May 13, 2009 9:05 AM

Olivia Thergood, Daniel Maloney, Katiria Lopez said...

Olivia Thergood

Daniel Maloney

Katiria Lopez

Physics Per. 1

Sound Waves

1. Wavelength = velocity / frequency

= 340 m/s / 1000 Hz

= .34

2. Cancellation would not occur with stereo sound.

May 14, 2009 9:59 AM

Paige, Beth, Erica said...

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.

Summary

A stone dropped in water causes a disturbance to travel outward in an expanding circle. The water doesn't go anywhere; it is only the energy which moves.

V= (gd)^1/2

If a succession of stones were dropped, one each second, a wave train would be created. The expanding circles in the wave train are called wave fronts.

1.) One stone is dropped into the water every 1/5 second. What are the period and frequency of the wave motion?

Period = 1/5 second

Frequency = 1 / (1/5) = 5 Hz

The distance between the maxima is called the wavelength of the wave.

Distance = speed x time

Wavelength = wave speed x period

Assuming the wave speed of the disturbance on water is 2 m/s, and the period of the wave motion is 1/5 s, what is the wavelength of the wave motion?

Wavelength = (2 m/s) x (1/5 s) = 0.4 m

Longitudinal: displacements are parallel to direction of propagation. Transverse: displacements perpendicular to propagation direction Compressions are regions of above-normal air pressure. Rarefactions are regions of below-normal air pressure.

2.) The speed of sound in air is about 340 m/s. What is the wavelengh of sound created at 1000 Hz?

Waverlength = (340) x (1000) = 340000

Ultrasound is sound at a frequency which is outside of the range of human hearing. Sound travels faster in warm air. When compressions from one source overlap rarefactions from another, cancellation occurs. Beat frequency

is the difference between the frequencies of the two tuning forks.

Positions of zero rope displacement in a standing wave are called nodes. At each end of any loop there is a node, and two loops makes one wavelength. Distance between adjacent nodes is one-half wavelength.

Doppler Effect - Approaching, the frequency of a sound is higher because the wavefronts are closer together

in time. Departing, the frequency is lower. Sounds are a mixture of the fundamental and one or more of the overtones. These mixtures are called composite vibrations.

May 14, 2009 10:01 AM

Yesenia Llanos, Niccolai Arenas, Ashley Lynk, Catalina Estrada, Nataliya Kushta said...

• Move the amplitude slider back and forth to see its effects on all parts of the wave. What happens?

The amplitude changes the height of the crests and the depth of the troughs, but not the wavelength or velocity.

• Move the Wavelength slider back and forth to see its effect on all parts of the wave. What happens?

The wavelength changes the distance between neighboring crests and troughs, but not the amplitude or velocity.

• Where is the other red particle at this moment?

There at the same height.

• Where is the yellow particle at this moment?

At the lowest point.

• Where is the other red particle at this moment?

At the lowest point.

• Where is the yellow particle at this moment?

At its highest point.

• How far apart are the two red particles?

One wavelength.

• How far apart are the red and yellow particles?

Half a wavelength.

• Which ones get through both of the circular filters?

The vertical ones

• What happens to the vertical waves now?

They don’t pass through the filter

• What happens to the horizontal waves now?

They get through the first filter but don’t go through the second one.

• How could you allow the horizontal waves to get through the second filter?

By rotating it 90 degrees.

• Look at the length of the wave on the scale. How far did the wave travel?

24 m

• What is the connection between the numbers in each row of the table?

velocity = frequency X wavelength

• Which way is the wave moving?

Left to right

• Look at the particles in the material. How is their disturbance different to the way they are disturbed by a transverse wave?

Here the particles go from left to right.

• 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

• What is the amplitude now?

0.25 cm.

• How did you do this?

By increasing the amplitude.

• Assuming the vertical background lines are 1 cm apart, what is the distance between the centres of two neighbouring compressions?

10 cm.

• What is the distance between the centres of two neighbouring rarefactions?

10 cm

• How does this compare to the distance between compressions?

It is the same.

• What is the wavelength now?

About 13 cm

• What is the amplitude of the wave?

0.5 cm

• What is the wavelength of the wave?

10 cm

• What has happened to the velocity of the wave?

Increases

• What is the amplitude of the wave now?

0.5 cm

• What is the wavelength of the wave now?

10 cm

• What do you notice about the amplitude and wavelength of the wave as the velocity changes?

Amplitude and wavelength stay the same.

• Using this information, why do you think you see a lightning flash before hearing thunder?

Light travels faster than sound.

• Find the minimum wavelength value.

5 cm

• What is the maximum wavelength value?

20 cm

• How do they move?

Back and forth

• 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?

They move closer to the layer.

• 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?

They moved further from the layer.

• From the graph, what is the approximate displacement of the green layers at the middle of a compression?

Zero

• From the graph, what is the approximate displacement of the red layers at the middle of a rarefaction?

Zero

• When the displacement graph is positive, which way have the particles been displaced from their rest positions?

To the right.

• When the displacement graph is negative, which way have the particles been displaced from their rest positions?

To the left.

• How does this affect the air pressure?

Decreases

• What is the height in divisions of the crest of the wave on the screen?

Two

• What is the amplitude of the wave, in volts?

2 × 0.2 = 0.4 V

• What is the wavelength, in divisions, of the wave on the screen?

Four

• What time is represented by the wavelength value?

4 × 0.5 = 2 ms = 2/1000 in seconds

• Use this equation to calculate the frequency of the sound you see being displayed on the oscilloscope screen.

1000/2 = 500 Hz

• What is the periodic time and the frequency of this sound?

About 12 ms and 80 Hz.

Combining Waves

• How do their amplitudes and wavelengths compare?

They are the same.

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

They are in phase.

• How do these two waves compare in amplitude and wavelength?

They are the same.

• 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 many times does this resonance happen?

Four

• 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

• 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?

It is three times as long.

• Repeat the experiment and see how many resonant positions you can find. How many are there?

Three

• 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?

The wave spreads around the edges of the 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?

There are two regions where the wave crests are missing.

• What would you expect to happen where two wave crests meet?

A very high crest would be formed.

• What would you expect to happen where two wave troughs meet?

A very 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 crest of one wave is cancelled out by the trough of the other one, leaving the water calm.

• What happens at the point marked with a red dot?

A wave crest from source 1 has met a crest from source 2 so they reinforce and make a high crest.

• What is the difference between your two answers in terms of wavelengths?

A wave crest from source 1 has met a crest from source 2 so they reinforce and make a high crest.

• 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.

May 14, 2009 10:32 AM

Lucas, Vince, Kelvine, Oscar, Abdou said...

Vince Nguyen

Oscar Osorio

Lucas Leite

Abdou Williams

Kelvine Clarke

Wave Behavior

Which way are the reflected waves moving?

- Downwards, across the original wave.

How would you make the ripple tank produce waves of a smaller wavelength?

- make the motor run faster so that the wooden beam vibrates more frequently.

What happens to the plane wave after reflection?

- it becomes a circular wave.

What happens to the curved reflected waves?

- They get smaller and concentrate into a point.

What shape does the reflected wave have?

- a circular shape.

Where doe the reflected waves seem to come from?

- They seem to come from a point behind the reflector that is the same distance from it as the original source of the waves.

What happens to the wave?

- the wave changes direction when it enters the shallow water.

What happens to the speed of the waves?

- the wave speed is less in the shallow water.

What happens to the wavelength?

- the wavelength is reduced in the shallow water.

Which way is the wave moving?

- from left to right.

Focus on any particle. Which way are the particles moving?

- from up to down.

Assuming the background lines are 1 cm apart, how high is your wave above the black centre line?

- 1cm

What is the amplitude now?

- 7.5 cm

What is the amplitude of the wave?

- 5 cm

Assuming the background lines are approximately 1 cm apart, what is the distance between two wave tops?

- 15 cm

Move the wavelength slider to the left. What happens?

- the wave crests get closer together.

What is the wavelength now?

- 10 cm

What is the wavelength now?

- 20 cm

What is the amplitude now?

- 5 cm

Have you changed the energy carried by the wave? Explain your answer.

- no, because the wave amplitude has not changed.

What is the amplitude of the wave and what is its wavelength?

- Its amplitude is 5 cm and its wavelength is 15 cm.

What has happened to the velocity of the wave?

- it has increased.

Click pause and measure the amplitude of the wave and wavelength agaian. Have they changed?

- no

Move the Amplitude slider back and forth to see its effect on all parts of the wave. What happens?

- The amplitude changes the height of the crests and the depth of the troughs, but not the wavelength or velocity.

Move the wavelength slider back and forth to see its effects on all parts of the wave. What happens?

- the wavelength changes the distance between neighboring crests and neighboring troughs, but not the amplitude or velocity.

Where is the other red particle at this moment?

- at the same height.

Where is the yellow particale at this moment?

- at its lowest point.

Where is the other red particale at this moment?

- at its lowest point.

Where is the yellow particale at this moment?

- At its highest point.

How far apart are the two red particales?

- one wavelength.

How far apart are the red and yellow particales?

- half a wavelength.

Which ones get through both of the circular filters?

- the vertical ones.

What happens to the vertical waves now?

- they cannot pass through the filter.

What happens to the horizontal waves now?

- they get through the first filter but not the second one.

How could you allow the horizontal waves to get through the second filter?

- by rotating it 90 degrees.

Look at the length of the wave on the scale. How far did the wave travel?

- 24 m

What is the connection between the numbers in each row of the table?

- velocity = frequency x wavelength.

Which way is the wave moving?

- from left to right.

Look at the particales in the material. How is their disturbance different to the way they are disturbed by a transverse wave?

- Here the particles are disturbed from left to right, rather than up to down.

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

What is the amplitude now?

- about 0.25 cm

How did you do this?

- by increasing the amplitude.

Assuming the vertical background lines are 1 cm apart, what is the distance between the centres of two neighboring compressions? (particles at the center of each compression should be on, or close to a vertical line.)

- approximately 10 cm.

what is the distance between the centers of two neighboring rarefactions?

( again, particles at the center of each rarefactions should be on, or close to a vertical line.)

- approximately 10 cm.

How does this compare to the distance between compression?

- it is the same.

Click pause to pause the wave. What is the wavelength now?

- about 13 cm.

what is the wavelength of the wave?

- 0.5 cm

What is the wavelength of the wave?

- 10 cm

What has happened to the velocity of the wave?

- it has increased.

What is the amplitude of the wave now?

- 0.5 cm

What is the wavelength of the wave now?

- 10 cm.

What do you notice about the amplitude and wavelength of the wave as the velocity changes?

- amplitude and wavelength stay the same.

Using this information, why do you think you see a lightning flash before hearing thunder?

- because light travels much faster than sound.

Click pause and find the minimum wavelength value.

- 5 cm

What is the maximum wavelength value?

- 20 cm.

How do they move?

- back and forth either side of their rest position.

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?

- they have moved closer to this layer.

- they have moved further from this layer.

From the graph, what is the approximate displacement of the green layers at the middle of a compression?

- zero

From the graph, what is the approximate displacement of the red layers at the middle of a rarefaction?

- zero

when the displacement graph is positive, which way have the particles been displaced from their rest positions?

- to the right.

When the displacement graph is negative, which way have the particles been displaced from their rest positions?

- to the left.

How does this affect the air pressure?

- it reduces it.

What is the height in divisions of the crest of the wave on the screen?

- two divisions.

What is the amplitude of the wave, in volts?

- 2 x 0.2 = 0.4 v

What is the wavelength, in divisions, of the wave on the screen?

- four divisions.

What time is represented by the wavelength value?

- 4 x 0.5 = 2 ms = 2/1000 in seconds

Use this equation to calculate the frequency of the sound you see being displayed on the oscilloscope screen.

- 1000/2 = 500 hz.

What is the periodic time and the frequency of this sound?

- about 12 ms and 80 hz.

Combining Waves

Vince Nguyen

Oscar Osorio

Lucas Liete

Abdou Williams

Kelvine Clarke

How do their amplitudes and wavelengths compare?

- they are the same.

Are the waves in phrase or out of phrase with each other?

- in phase.

How do these two waves compare in amplitude and wavelength?

- They are the same.

Are they in phase or out of phase with each other?

- theya re out of phase. The crests of one wave line up with the troughs of the other.

Predict what will happen when two waves are added.

- they will 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 a wavelength.

When the red and blue waves are in phase are they added constructively or destructively?

- Constructively

How many times does this resonance happen?

- four

What are the frequencies?

- 15, 20, 45, and 60 units.

How many antinodes are seen at each of these frequencies?

- one, two , three, and four antinodes, respectively.

What is the ration 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 value, what is the wavelength of the sound you have heard?

- 4 x 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 x 0.860 = 330 m s ^-1

How does this length compare with the first one?

- it is three times as long.

Repeat the experiment and see how many resonant positions you can find. How many are there?

- three.

From the length of the second one, where there are three node- antonode distances, what is the wavelength and the velocity of the sound?

- 0.688 m and 330 m s ^-1

What happens to the wave?

- the wave spreads around the edges of the two obstacles.

What difference do you see in the waves that diffract through the narrow gap?

- the waves are diffracted through the wider angle when they pass through a narrow gap.

What do younotice about the area to the right of the barrier compared to the single – slit picture?

- these are two regions where the wave crests are missing.

What would you expect to happen where two wave crests meet?

- a very high crest would be formed.

Now look for places where a crest from one wave source meets a through from the other. What would you expect to happen in these places?

- the crest of one wave is cancelled out by the through of the other one, leaving the water calm.

What would you expect to happen where two wave throughs meet?

- a very low through would formed.

Now look for places where a crst from one wave source meets a through from the other. What would you expect to happen in these places?

- the crest of one wave is cancelled out by the trough of the other one, leaving the water calm.

What happens at point marked with a red dot?

- a wave crest from source 1 has meet a crest from source 2 so they reinforce and make a high crest.

What is the different 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 through from the other.

What do these straight lines represent?

- regions of cancellation where crests from one source meet throughs from the other.

What does this do to x?

- increasing the source separation a decreases x.

what does this do this x?

- increasing the wavelength increases x.

what does this do to x?

- increasing the distance to the cross section sections increases x.

May 14, 2009 10:39 AM