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 04-17-08, 09:20 PM #1 BenLi Hardrocker Thread Starter   Join Date: Jul 2007 Bikes: Posts: 1,569 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) Physics Help???? PLEASE!?!?!?! Alright, this is basic stuff, but I'm REALLY struggling with it, so if anyone could shed some light on these issues, it would be appreciated: 1) Find the binding energy of N-13 nucleus, if the isotope of N-14 is more stable, what is the equation for the expected decay reaction. Okay so, for this question, I can get the binding energy part easily by using E=mc^2, but it's the latter part of the question I don't understand. We only learned about alpha, Beta (2 types), and gamma decay. None of those will get the N-13 to N-14 2.) The half-life of N-13 is 10 min. If a sample contains 3.3 * 10^ 12 at t = 0, how many N-13 nuclei are still present 40 min. later? And this one... is just a blur...
 04-17-08, 09:25 PM #2 Mr. Underbridge Senior Member   Join Date: Mar 2007 Location: Reston, VA Bikes: 2003 Giant OCR2 Posts: 2,369 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 3 Post(s) On #1, I don't think the question is asking what you think it is. N-13 can't decay to N-14 because N-14 has an extra neutron. On #2, the half life is exactly what it claims to be - the time after which half the stuff is still there. How many half lives have passed 40 min later, and what does that mean? Hint: if half of it is gone after 10 minutes, it does *not* mean it's all gone after 20.
04-17-08, 09:41 PM   #3
Siu Blue Wind
I don't think so

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04-17-08, 09:47 PM   #4
BenLi
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 Originally Posted by Mr. Underbridge On #1, I don't think the question is asking what you think it is. N-13 can't decay to N-14 because N-14 has an extra neutron. On #2, the half life is exactly what it claims to be - the time after which half the stuff is still there. How many half lives have passed 40 min later, and what does that mean? Hint: if half of it is gone after 10 minutes, it does *not* mean it's all gone after 20.
1. So what do you think this question is asking for?

2. Then, 1/16 of it is still there?

 04-17-08, 09:54 PM #5 deraltekluge Senior Member     Join Date: Sep 2006 Bikes: Kona Cinder Cone, Sun EZ-3 AX Posts: 1,195 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) I have no idea, myself, but a little googling (http://en.wikipedia.org/wiki/Nitrogen) tells me that Nitrogen 13 will decay to Carbon 13 via the emission of a positron. As Mr. Underbridge says, "half life" is the time it takes for half the atoms to decay. So, after 10 minutes, half the original atoms have decayed and half remain; after 20 minutes, half of those have decayed and a quarter of the original atoms remain; after 30 minutes, an eighth remain; and after 40 minutes, a sixteenth.
 04-17-08, 10:04 PM #6 bluebottle1 Kicked out of the Webelos     Join Date: Apr 2005 Bikes: Posts: 239 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) On the other hand, if a chicken and a half can lay an egg and a half in a day and a half, how long would it take a grasshopper with one wooden leg to kick all the seeds out of a dill pickle? __________________ ______________________________________________ Kicked out of the Webelos.
 04-17-08, 10:30 PM #7 iamlucky13 Footballus vita est     Join Date: Jun 2002 Location: Portland, OR Bikes: Trek 4500, Kona Dawg Posts: 2,118 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) Regarding #1, I think the statement that N-14 is more stable is just a hint that N-13 won't tend to reduce in neutrons while still remaining nitrogen. In other words, I think you can discount beta decay. And gamma decay isn't really a decay, it's a photon emission. Actually, looking up isotopes of nitrogen on wikipedia, this one has me slightly confused. __________________ "The internet is a place where absolutely nothing happens. You need to take advantage of that." ~ Strong Bad
04-17-08, 10:32 PM   #8
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 Originally Posted by bluebottle1 On the other hand, if a chicken and a half can lay an egg and a half in a day and a half, how long would it take a grasshopper with one wooden leg to kick all the seeds out of a dill pickle?
A: Peoria Illinois
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04-17-08, 10:38 PM   #9
bluebottle1
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 Originally Posted by Wordbiker A: Peoria Illinois
Damn, but you're good.
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 04-17-08, 11:08 PM #10 goldfishin Senior Member   Join Date: Mar 2007 Bikes: Posts: 521 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) just look in the book. or ask the science help lab guys.
 04-17-08, 11:20 PM #11 BenLi Hardrocker Thread Starter   Join Date: Jul 2007 Bikes: Posts: 1,569 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) Thanks everyone, I think the consensus is that it's a Beta plus decay, my formula ended up looking like this n-13 -----> Carbon-13 + positron + neutrino
04-18-08, 04:58 AM   #12
Tom Stormcrowe
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 Originally Posted by Wordbiker A: Peoria Illinois
Wordbiker, you and your Illinois Physics triggered an earthquake
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04-18-08, 11:06 AM   #13
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 Originally Posted by Tom Stormcrowe Wordbiker, you and your Illinois Physics triggered an earthquake
Yeah, that was a bit uncanny.

I've never even been to Peoria...it just popped into my head. I was born in CA so I've been through my share of earthquakes. It's scary even when you're somewhat used to them.
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 04-18-08, 05:03 PM #14 EJ123 djentleman     Join Date: Aug 2005 Bikes: Posts: 3,370 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 5 Post(s) Private Message JSchen. He'll know.
 04-18-08, 10:47 PM #15 ManBearPig 1/2 man,1/2 bear,1/2 pig     Join Date: May 2004 Location: . Bikes: . Posts: 1,122 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) F does not equal MA. F equals M times the integral of dv/dt. It doesn't answer your question, but it's good to know for extra credit. __________________ ...
04-18-08, 11:46 PM   #16
deraltekluge
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 Originally Posted by ManBearPig F does not equal MA. F equals M times the integral of dv/dt. It doesn't answer your question, but it's good to know for extra credit.
Huh? F=ma, a=dv/dt, v is the integral of a.

 04-18-08, 11:59 PM #17 Sixty Fiver Bicycle Repair Man !!!     Join Date: Sep 2007 Location: YEG Bikes: See my sig... Posts: 27,280 Mentioned: 7 Post(s) Tagged: 0 Thread(s) Quoted: 28 Post(s) Did you all hear that sound ? That was my brain exploding. Basic stuff.. yuh huh. __________________ ravingbikefiend.com / Winter Cycling 101 / RBF Cycles / My Bicycles / Sales