Biphysics Homework: Wrong Answer of P2/P1=R1/R2?

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Homework Help Overview

The discussion revolves around a physics problem related to pressure ratios and their relationship with radius ratios, specifically questioning the validity of the formula p2/p1 = r1/r2. Participants are exploring the context of fluid dynamics or wave physics.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants are questioning the correctness of the formula p2/p1 = r1/r2 and discussing alternative formulations, including p2/p1 = (r1/r2)^2 and p2/p1 = (r1/r2)^3, particularly in the context of shock waves. There are inquiries about units and unit conversion factors, as well as the behavior of over-pressure with distance.

Discussion Status

The discussion is active, with participants expressing uncertainty about the initial formula and exploring alternative relationships. Some guidance has been offered regarding potential correct formulas, but no consensus has been reached.

Contextual Notes

There appears to be confusion regarding the appropriate formula to use, and participants are considering the implications of different assumptions related to the physics involved.

iram
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Homework Statement
Introduction to Biophysics homework
Relevant Equations
A pistol shrimp creates short, strong pressure waves by clicking its enlarged claw, and uses these blasts to stun small fish. The click is measured to produce a pressure wave with an amplitude of 80 kPa at the distance of 4cm from the claw. An explosion can be considered to by potentially fatal for humans when the pressure amplitude is approximately 20 Psi. At what distance from the shrimp is the click of the claw fatal for a diver? What is the total power of the click?
Is it done by using the formula p2/p1= r1/r2? I got answer 2.3 cm but it comes out it is wrong. Why?
 
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What are the units? What are the unit conversion factors? Over-pressure drops off with what function of distance?
 
iram said:
the formula p2/p1= r1/r2?
That does not look right to me. I would have guessed ##\frac{p_2}{p_1}=(\frac{r_1}{r_2})^2##, but from what I read online it is even ##\frac{p_2}{p_1}=(\frac{r_1}{r_2})^3## for a shock wave.
 
Yes, I think I get it now. The formula really doesn't look correct. I believe the one you mentioned above is the right one to use. Thank you :)
 

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