How far away is the farmer? Speed of sound and wave vibration in physics

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    Sound Vibration Wave
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Discussion Overview

The discussion revolves around a physics problem involving sound, vibration, and wave propagation. Participants explore the scenario of a farmer hammering a stake and the implications of sound travel time in relation to visual observation.

Discussion Character

  • Homework-related
  • Conceptual clarification
  • Mathematical reasoning

Main Points Raised

  • One participant asks for help in solving a problem about determining the distance to a farmer based on the speed of sound and the timing of hammer blows.
  • Another participant suggests that the problem is straightforward and encourages the original poster to think through it.
  • One participant proposes that the distance is 330m based on the speed of sound and the time interval between hammer blows.
  • A different participant emphasizes the importance of understanding the process rather than just arriving at the correct answer, asking for clarification on the reasoning behind the proposed distance.
  • Another participant confirms that the original calculation of 330m is correct, explaining that the sound takes 1 second to travel the distance after the last blow.
  • Further, a participant introduces a modified scenario involving a wall, asking about the time change for sound travel and the implications for hearing the hammer blows under different conditions.

Areas of Agreement / Disagreement

Participants generally agree on the calculation of the distance to the farmer as 330m based on the given conditions. However, there are additional questions and scenarios introduced that remain unresolved, indicating ongoing exploration and debate.

Contextual Notes

The discussion includes assumptions about sound travel time and the effects of obstacles on sound propagation, which are not fully explored or resolved.

Who May Find This Useful

This discussion may be useful for students learning about wave mechanics, sound propagation, and problem-solving in physics contexts.

miyuki9
PHYSICS help please! Due 2morrow!

I'm learning about vibration and wave and sound. And I have to explain and solve this problem below, can someone please help me out...Thanks
You watch a distant farmer driving a stake into the ground w/ a sledgehammer. he hits the stake at a regular rate of one stroke per second. You hear the sound of the blows exactly synchronixed with e blows u see. And then you hear one more blow after u see him stop hammering. How far away is the farmer? (speed of sound is 330m/s)
 
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Wow, if questions were always this easy...

...I might have been a physicist.

Hello miyuki9,
Just think about it for one second and maybe it will come to you...
 
is it 330m? Is that right?
 
I think it is better to understand the process and make a simple mistake that gives a wrong answer than it is to have the correct answer and misunderstand how you got it.

Can you explain your thinking to arrive at that figure?
 
b/c u see and hear the sound @ the same time, according to the problem, so I take 330m/s * 1s = 330m.
if I'm wrong or misunderstood, Plz explain and show me how to do it please!
 
You have done fine!
You were given the exact time between hammer-blows (1 second), but the most important hint is that you hear the sound 1-sec after the last blow. That means it must take 1-sec for the sound to travel the distance from the hammer to your ears. Knowing how fast sound travels let's you set up the problem just as you have done; (330m/s)(1s)
You end up with ‘s’ in both the numerator and denominator of the equation where they cancel out (to 1), leaving you with 330m as the distance.

Pretty cool, huh?
 
Last edited by a moderator:
You are correct. You are hearing each hit exactly one second after it happens. Thus because you hear it at 300m/s, he must be one second-unit of sound away. Thus 330m

I think the physics people here, me included, don't like to just give an answer, as it doesn't promote the learning process. I agree.

So, If this farmer was at the same distance from you. But there was a small wall in front of you, and an infinite one behind you, so the sound goes from farmer to large wall and back to you. And the distance of the large wall from you another 660m.

What is the time change between the sound for the farmer and the time you hear it?

How many hits will you hear after the farmer stops hitting?

HARDPART: At what speed would the farmer have to run from where he is hitting to you, in order to hear the last hit at your location? heh, answer it and you get a cyber-kiss.
 
Brrr! Cold day.
 
Originally posted by Integral
Brrr! Cold day.
Indeed!
 

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