From key@physics.utoronto.ca Sun Apr  6 21:01:38 2008
Date: Sun, 06 Apr 2008 21:01:39 -0400
From: Tony Key <key@physics.utoronto.ca>
To: xiao.ou@utoronto.ca
Subject: Re: Mastering physics practice problem 6

Hi Xiao - You can use V=(R/r)v to find the activity that the sample would
have had at time t=0.  You can then write down two equations, that tell you
what the activity of both samples when they are measured.  One has been in
the body for 24 hours (nuclear plus be) then sits for 26 hours (nuclear
only) till it's measured.  The other stays in the body for 48 hours (n + be)
and then suffers only nuclear decay for the remaining two hours.  These are
two simultaneous equations in lambda_n and lambda_be - you know all the
activities - remember to subtract the background from the measured ones.

This problem is quite hard, so don't  worry about it too much.

I won't have time to go over it in class.  If you are determined to
understand it, come and see me!

Tony

xiao.ou@utoronto.ca wrote:
> Hi sir. This is Xiao. I've tried doing question 6 and got stuck  thinking
> about it. Even after reading the hints and the questions  already asked on
> the bulletin, I'm not too sure how to approach it.
> 
> I know that we need to find lamda(eff) and lamda(unclear) and to do so  we
> have to use the decay equations. But in the hints it says that  lamda(eff)
> is only considered with the decay in the body.
> 
> so what I thought was both the samples have had decay in the body  before
> being taken out, so to find lamda(nuclear) we can use the 24  hour sample,
> taking that it has been sitting for 26h before it was  counted. But at the
> same time I don't know what the activity is right  when it is taken from
> the body. I don't think we can use the V=(R/r)v  relation since the
> activity is affected by nuclear and biological decay.
> 
> I'm really stuck on this question. It would be nice if you could maybe  go
> over it on the review class monday? I know it's a bit late asking  this.
> But if not could you possibly give me a few hints on how to  solve it?
> Thanks
> 
> 
> Xiao
> 

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