1. How many nodes (counting nodes at the ends), are present in the displacement oscillations of an open-closed tube (oboe) that vibrates in its fourth harmonic?

a) 3 nodes
b) 4 nodes
c) 5 nodes
d) 6 nodes
e) An open-closed tube has no 4th harmonic

2. At a distance of 30 m the noise from the engine of an jet has an intensity of 130 dB. At this level, you will be in pain and your ears will hurt. That's why this intensity is know as the "pain threshold". How far do you have to move from the jet in order for the noise to drop down in intensity to 57.9 dB, a level comparable to that of a spoken conversation?

3. An out-of-tune violin plays an "A" note of 446 Hz. At the same time, a tuning fork vibrates with a true-A of 440 Hz. The frequency of the beats produced (intensity fluctuations) is ...
***Hint: The frequency of the beats is not the same as the frequency of the envelope.***

a) No beats are produced in this situation
b) 1.5 beats per second
c) 3 beats per second
d) 6 beats per second
e) 12 beats per second

get a life and do bayer's online homework yourself!

1) e!

3) d (6 beats per s) formula: f_beat = |f1-f2|

at above person..lol! what were you doing here yourself..if not searching for help to do these questions?

1. To answer this question, we need to understand the concept of harmonic frequencies in vibrational systems such as open-closed tubes. The fundamental frequency is the lowest frequency at which a tube can resonate, and each harmonic frequency is a multiple of the fundamental frequency.

In an open-closed tube, the harmonic frequencies are odd multiples of the fundamental frequency. The fundamental frequency has one node at each end, and each subsequent harmonic frequency adds one additional node.

So, in the fourth harmonic, there will be three additional nodes besides the two nodes at the ends (one for each odd multiple of the fundamental frequency). Therefore, the answer is:

a) 3 nodes

2. To answer this question, we need to know the relationship between sound intensity and distance from the sound source. In general, sound intensity follows the inverse square law, which means that as you move further away from the source, the intensity decreases proportionally to the square of the distance.

To calculate the distance needed for the noise to drop from 130 dB to 57.9 dB, we can use the formula:

I₁/I₂ = (r₂/r₁)²

Where I₁ and I₂ are the initial and final intensities, and r₁ and r₂ are the initial and final distances.

Plugging in the values, we get:

130 dB/57.9 dB = (30 m/r₂)²

Simplifying the equation, we find:

(130/57.9) = (30/r₂)²

Solving for r₂, we get:

r₂ = √[(30² * 57.9)/130]

Calculating this value, we find that r₂ is approximately 10.04 meters.

So, you would need to move approximately 10.04 meters away from the jet for the noise to drop down to a level comparable to that of a spoken conversation.

3. To answer this question, we need to understand the concept of beats. Beats occur when two sound waves of slightly different frequencies interfere with each other, resulting in periodic variations in the amplitude (intensity) of the combined wave.

The frequency of the beats can be calculated by taking the absolute value of the difference between the two frequencies. In this case, the frequency of the beats will be:

|446 Hz - 440 Hz| = 6 beats per second

So, the correct answer is:

d) 6 beats per second