I have a few questions that i am not too sure how to figure out...
1- as a racing car zooms by you, its pitch decreases by 20%. If the speed of sound is 345m/s, how fast is the car travelling?
2-a person has a threshold of hearing of 5db. another person has a threshold of hearing of 25db. Which person has better hearing and by how much?
PLEASE HELP! :(
1. Solve (a+V)/(a-V) = 0.8
a is the speed of sound, and V is the car's speed.
2. The person who can hear the lower 5 dB level has better hearing, by 20 dB. That is a factor of 100 times less in sound power level
I do not really know but somthing to do with isolating Vo ?
Sure! I can help you with these questions. Let's break them down step by step.
1. To find the speed of the car, we need to use the concept of the Doppler Effect. The Doppler Effect explains how the frequency and pitch of sound waves change as the source of the sound moves relative to an observer.
The formula we need to use for this problem is:
f' = f * (v + v_obs) / (v + v_source)
Where:
f' is the observed frequency (decreased pitch after the car zooms by)
f is the original frequency
v is the speed of sound (given as 345 m/s in this case)
v_obs is the velocity of the observer (assumed to be zero for this problem since it is not mentioned that the observer is moving)
v_source is the velocity of the source (the speed of the car)
Given that the pitch decreases by 20%, we can set up the equation as follows:
f' = f - 0.2f
Substituting the known values into the formula and equation, we get:
f - 0.2f = f * (345 + 0) / (345 + v_source)
Simplifying the equation, we have:
0.8f = f * 345 / (345 + v_source)
Now, let's solve for v_source:
0.8 = 345 / (345 + v_source)
Cross-multiplying and rearranging the equation, we have:
0.8(345 + v_source) = 345
276 + 0.8v_source = 345
0.8v_source = 345 - 276
0.8v_source = 69
v_source = 69 / 0.8
v_source = 86.25 m/s
Therefore, the car is traveling at approximately 86.25 m/s.
2. To determine which person has better hearing and by how much, we need to compare their threshold of hearing values.
The threshold of hearing is the minimum sound intensity that a person can hear. The lower the value, the better the hearing ability.
In this case, the person with a threshold of hearing of 5 dB has better hearing because it is a lower value compared to the person with a threshold of hearing of 25 dB.
The difference between their thresholds of hearing is calculated by subtracting the higher value from the lower value:
Difference = Threshold of Hearing (Person 1) - Threshold of Hearing (Person 2)
= 5 dB - 25 dB
= -20 dB
Therefore, the person with a threshold of hearing of 5 dB has better hearing than the person with a threshold of hearing of 25 dB by 20 dB.
Of course, I'll be happy to help you with these questions!
1- To determine the speed of the car, we need to use the concept of Doppler effect. The Doppler effect is the change in frequency or pitch of a sound wave due to the relative motion between the source of the sound and the observer.
In this case, the car is the source of the sound, and you are the observer. The pitch of a sound is directly related to its frequency. Since the pitch decreases by 20%, it means the frequency of the sound decreases by 20%.
To calculate the speed of the car, we can use the following formula:
v = (vf - vo)/vo
where v is the speed of the car, vf is the final frequency (after the pitch decrease), and vo is the initial frequency (before the pitch decrease).
Since frequency is inversely proportional to wavelength, we can also express the formula as:
v = (λo - λf)/λf
where λo is the initial wavelength (before the pitch decrease), and λf is the final wavelength (after the pitch decrease).
Given that the speed of sound is 345 m/s, we can use this information to find the answer.
2- To determine which person has better hearing, we need to compare their respective thresholds of hearing.
The threshold of hearing is the smallest sound intensity that a person can perceive. The unit for measuring sound intensity is decibels (dB). A lower threshold of hearing means that the person can hear sounds with lower intensity, indicating better hearing.
In this case, the first person has a threshold of hearing of 5 dB, while the second person has a threshold of hearing of 25 dB. Therefore, the first person has better hearing, as their threshold of hearing is lower by 20 dB (25 dB - 5 dB = 20 dB).
I hope this helps! Let me know if you have any other questions.