# Foo - Physics Help???? PLEASE!?!?!?!

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View Full Version : Physics Help???? PLEASE!?!?!?!

BenLi
04-17-08, 10:20 PM
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...

Mr. Underbridge
04-17-08, 10:25 PM
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.

Siu Blue Wind
04-17-08, 10:41 PM

I'm outta here.

BenLi
04-17-08, 10:47 PM
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?

deraltekluge
04-17-08, 10:54 PM
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.

bluebottle1
04-17-08, 11:04 PM
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?

iamlucky13
04-17-08, 11:30 PM
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.

Wordbiker
04-17-08, 11:32 PM
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

bluebottle1
04-17-08, 11:38 PM
A: Peoria Illinois

Damn, but you're good.

goldfishin
04-18-08, 12:08 AM
just look in the book. or ask the science help lab guys.

BenLi
04-18-08, 12:20 AM
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

Tom Stormcrowe
04-18-08, 05:58 AM
A: Peoria Illinois

Wordbiker, you and your Illinois Physics triggered an earthquake :p

Wordbiker
04-18-08, 12:06 PM
Wordbiker, you and your Illinois Physics triggered an earthquake :p

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.

EJ123
04-18-08, 06:03 PM
Private Message JSchen. He'll know.

ManBearPig
04-18-08, 11:47 PM
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.

deraltekluge
04-19-08, 12:46 AM
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.

Sixty Fiver
04-19-08, 12:59 AM
Did you all hear that sound ?

That was my brain exploding.

Basic stuff.. yuh huh.