Joseph Renna

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2 Badges

14 years, 42 days

I am currently a Physics student at the University of Massachusetts at Boston, MA USA.

I am studying Applied Physics, and specializing in computational physics as well as underwater acoustics.


MaplePrimes Activity

These are answers submitted by Joseph Renna

Thanks for all your help Adnan. I factored them the way I wanted by hand. Yes, I can see how it would be ambiguous in this case, since they could be factored in terms of the z's or the amplitudes.

All the best,


Thank you for the replies, Adnan. i couldn't read the first wordpad doc, my wordpad doesn't have a zoom function, and I don't have MS Word on this machine. but your worksheet enlightened me with some cool tricks, like extract... I didn't know I could do that. Actually, I worked out the equations by hand over the weekend, and also have a reference to check my answers.

So, instead of solving all 4 equations for the 4 unknowns, we can do 2 at a time, since these are the boundary conditions for sound transmission thru 3 media. But now I have another problem. I can't seem to factor my solutions, Maple just keeps returning the same equation. I show this in the attached worksheet. At least my machine is not hanging any more.. Check out the worksheet, and if you know what I am doing wrong, pls let me know. Capital I, huh, well, the engineers use j, so I guess I can get used to that. ;-)

Thanks and have a great holiday yourself... I am already trying to get a 'jump' on next semester


Download Attached File

I've re-attached the document.

Feel free to ask me any questions about the worksheet :)

 Thank you, I have class this PM, but I will look it over tonite when I get back from school. I was able to download it this time. I will let you know if I have any questions. Thanks again.


- OK, so while I was looking over your worksheet, I realized I had made an error. I dropped the mass term from the left side in equation 1.

So I re-solved the whole thing again. Now, as I am checking it over, it looks like the square of the mass is under the radical. When I plug in numbers, my suspicions are correct. My assigned project is to simulate a meteor entering the atmosphere (at zinitial=120Km), experiencing

quadratic drag friction, and ultimately landing on the surface of the earth, and compute the heating, ablation, terminal velocity, energy release, crater size and all that. In this course, we have to program in FORTRAN 77, and visualize with matlab. The mass of the meteor is on the order of 2e13Kg, so it dwarfs all the other terms under the radical, e.g. Cd~0.5, zi and z(i-1) are very small compared with 10^13.  I don't know if you are familiar with this topic at all. This is the first time I have worked with quadratic air drag. So now I am thinking this is all about velocity. I am going to try a few things with that. If you have any suggestions, I would be happy to hear from you. Again, thank you very much for helping me with my initial problem. Your worksheet and explanation was excellent.



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