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Synchromesh
Original Poster
1,538 posts
36 months
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Is the last step correct?
The formula for radioactive activity is;
If A = A(0) e ^ - lamba t
Therefore
A/A(0) = e ^ - lamba t
Therefore
ln A/A(0) = lamba t
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Use Psychology
9,938 posts
62 months
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Another Fluffer
3,607 posts
35 months
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I think it's - lambda t.
Good luck to us both SM!
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Synchromesh
Original Poster
1,538 posts
36 months
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Hmm. For some reason in my notes I have it down without the minus. Does anyone else know?
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TheVole
167 posts
23 months
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I think you have to take natural logs (ln) of both sides to get rid of the e and stop the -lambda t being a power.
I'm assuming AQA physics, Monday morning?
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Another Fluffer
3,607 posts
35 months
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TheVole said: I'm assuming AQA physics, Monday morning? 
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TheVole
167 posts
23 months
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Another Fluffer said: TheVole said: I'm assuming AQA physics, Monday morning? Snap!
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McSam
4,956 posts
45 months
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Minus lambda t, with certainty. You can't just chuck signs away, my boy 
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David87
2,438 posts
82 months
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Hmm. I only did one day of A-level physics; now I remember why. Good luck, guys!
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Vilhelm
403 posts
19 months
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I've got it too.
I'm a bit useless when it comes to physics.
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Another Fluffer
3,607 posts
35 months
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Vilhelm said: I've got it too.
I'm a bit useless when it comes to physics. That makes 4 of us (that I'm aware of) Don't worry, so am I!
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Synchromesh
Original Poster
1,538 posts
36 months
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Another Fluffer said: That makes 4 of us (that I'm aware of)
Don't worry, so am I! And evidently we're all hard at work revising... Oh, and I'm useless at it too. Wish I'd never chosen it but that's another story for another day.
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Another Fluffer
3,607 posts
35 months
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Clearly! Story of my life.
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llewop
2,001 posts
81 months
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Synchromesh said: Is the last step correct?
The formula for radioactive activitydecay is;
If A = A(0) e ^ - lamba t
Therefore
A/A(0) = e ^ - lamba t
Therefore
ln A/A(0) = lamba t fixed that for you sorry - you get picky about things being right, especially as there are so many examples of messed up fomulae, units, definitions etc 
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Synchromesh
Original Poster
1,538 posts
36 months
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llewop said: Synchromesh said: Is the last step correct?
The formula for radioactive activitydecay is;
If A = A(0) e ^ - lamba t
Therefore
A/A(0) = e ^ - lamba t
Therefore
ln A/A(0) = - lamba t fixed that for you sorry - you get picky about things being right, especially as there are so many examples of messed up fomulae, units, definitions etc Ok. Except with the minus on the last formula right?
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Vilhelm
403 posts
19 months
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Synchromesh said: Another Fluffer said: That makes 4 of us (that I'm aware of)
Don't worry, so am I! And evidently we're all hard at work revising... Oh, and I'm useless at it too. Wish I'd never chosen it but that's another story for another day. I'm hard at work revising, I'll have you know. I just stared at a textbook for an hour. That's today's graft done.
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McSam
4,956 posts
45 months
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Synchromesh said: Ok. Except with the minus on the last formula right? Yes, ffs 
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spikeyhead
7,605 posts
67 months
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Of course there's a minus there, otherwise it wouldn't be decaying with time.
If you're not sure on a formula, do a quick plot of it in Excel and see the shape to see if it makes sense
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Another Fluffer
3,607 posts
35 months
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Vilhelm said: I'm hard at work revising, I'll have you know. I just stared at a textbook for an hour. That's today's graft done. My exact work ethic!
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Synchromesh
Original Poster
1,538 posts
36 months
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Another Fluffer said: Vilhelm said: I'm hard at work revising, I'll have you know. I just stared at a textbook for an hour. That's today's graft done. My exact work ethic! Ok, the dreaded question, how did it go for you guys?
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