radioactive substance, Physics

A certain radioactive substance has a half-life of 40 minutes. How much of an original 100 grams substance will remain after 2 hours?

solution) m= m0/2t/T

m=100 gms..

t=2 hours=2*60=120 min..

T=40 min

m=100/2120/40

m=100/23

m=100/8

m=12.5 gms.

Posted Date: 3/11/2013 3:35:59 AM | Location : United States





half life = 40minutes =2/3 hours

t(1/2)=(ln2 /k)

then k=(ln2/t(1/2)) = ln2/(2/3) = 3/2*(ln2)

origianl substance y0= 1000 grams

y=y0e-kt

y= 1000*(e-(3/2(ln2))*2 ) = 1000/8 = 125 grams

Posted by | Posted Date: 3/11/2013 3:37:25 AM


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