Determining Distance from Release Point Using Doppler Effect

In summary, the conversation is about a problem involving a tuning fork falling from rest and accelerating at 9.80 m/s2. The task is to determine how far below the point of release the tuning fork is when waves of frequency 488 Hz reach the release point, using the speed of sound in air as 343 m/s. The initial solution provided by the student was within 10% of the correct answer, but the system marked it as wrong. The conversation continues with a discussion on distinguishing between where the tuning fork was when the waves were emitted and when they reached the release point, and using the Doppler equation to find the speed of the emitted waves as the first step in solving the problem. The student then uses this information to
  • #1
lackos
38
0

Homework Statement


A tuning fork vibrating at 506 Hz falls from rest and accelerates at 9.80 m/s2. How far below the point of release is the tuning fork when waves of frequency of 488 Hz reach the release point? (Take the speed of sound in air to be 343 m/s).

Homework Equations


f(prime)=(v/(v+v(source)))*f(initial)
x=v(source)^2/19.6

The Attempt at a Solution


im actually fairly happy with my answer (8.17), because i worked it backwards from a textbook question, after it said i was wrong. but the system says i was wrong ( but within 10 percent).

any insight?

btw i subbed in my value for v(source) from question 1 into question 2 to get my answer.
 
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  • #2
Did you distinguish between:
(1) Where the tuning fork was when the 488 Hz waves were emitted
(2) Where the tuning fork was when the 488 Hz waves reached the release point
 
  • #3
Doc Al said:
Did you distinguish between:
(1) Where the tuning fork was when the 488 Hz waves were emitted
(2) Where the tuning fork was when the 488 Hz waves reached the release point

i thought that was already factored into the the doppler equation?
 
  • #4
lackos said:
i thought that was already factored into the the doppler equation
No. The Doppler equation will give you the speed at which the 488 Hz waves are emitted. That's just the first step in finding the answer. You need to figure out how long it takes for the sound to reach the top, then figure out where the tuning fork is at that time.
 
  • #5
Doc Al said:
No. The Doppler equation will give you the speed at which the 488 Hz waves are emitted. That's just the first step in finding the answer. You need to figure out how long it takes for the sound to reach the top, then figure out where the tuning fork is at that time.

okay thanks for that info (note to self).

so with my value (8.17), i would divide that by the speed of sound to get the extra time taken for travel. i would then form another kinematic equation factoring this in.

doing this i get 8.47m does this look correct
 
  • #6
lackos said:
okay thanks for that info (note to self).

so with my value (8.17), i would divide that by the speed of sound to get the extra time taken for travel. i would then form another kinematic equation factoring this in.

doing this i get 8.47m does this look correct
Looks good to me.
 
  • #7
Doc Al said:
Looks good to me.

thanks for the help and time
 

What is the Doppler effect?

The Doppler effect refers to the change in frequency of a wave (such as sound or light) as the source of the wave moves relative to the observer. This results in a perceived change in pitch or color.

How does the Doppler effect work?

The Doppler effect works by compressing the wavelengths of waves that are moving towards an observer and stretching the wavelengths of waves that are moving away from an observer. This results in a change in frequency and perceived pitch or color.

What causes confusion with the Doppler effect?

Confusion with the Doppler effect can be caused by a lack of understanding of how waves behave and the relationship between wavelength, frequency, and speed. Additionally, the effect can be counterintuitive, as the perceived change in frequency is dependent on the relative motion of the source and the observer.

How is the Doppler effect used in real life?

The Doppler effect has many practical applications, including in radar and sonar systems to detect the speed and direction of moving objects, in medical imaging techniques such as ultrasound, and in astronomy to measure the motion of stars and galaxies.

How can the Doppler effect be demonstrated?

The Doppler effect can be demonstrated with a simple experiment using a moving source (such as a toy car with a siren) and an observer (such as a person standing on the side of a road). As the source moves towards the observer, the siren will sound higher in pitch, and as it moves away, the siren will sound lower in pitch.

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