Activity - Physics

[mspeedwagon]

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I have the hang of half life problems, but am starting to see a few talking about activity. Wouldn't the answer to below just be 8330 decays per minute on the first day? Am I missing something?


Measurements of the radioactivity of a certain isotope tell you that the decay rate decreases from 8330 decays per minute to 3080 per minute over a period of 4.00 days. What is the activity of the isotope the first day?

 

[LoLCareerGoals]

Rate of change of decay rate = (3080 - 8330)/(4*24*60) = −0.911458333 decays/min^2 (deceleration of decay)
I don't understand the question though. What do you mean by activity? How many decays happened over the first day?
decays D1 = 8330*(24*60) −0.911458333*(24*60)^2/2 (just like constant acceleration equation)
decay rate at the end of day1?
decay rate@the end of D1 = 8330 - 24*60*0.911458333 or simply 8330 - (8330-3080)/4

 

[mspeedwagon]

I was a little confused by the question too. I think you are right. So the rate you get is basically in decays/min. Is that the rate that the isotope is decaying exactly after 24 hrs (slowed, but not to the final rate of decay). Just want to make sure I understand what was solved for.

Rate of change of decay rate = (3080 - 8330)/(4*24*60) = −0.911458333 decays/min^2 (deceleration of decay)
I don't understand the question though. What do you mean by activity? How many decays happened over the first day?
decays D1 = 8330*(24*60) −0.911458333*(24*60)^2/2 (just like constant acceleration equation)
decay rate at the end of day1?
decay rate@the end of D1 = 8330 - 24*60*0.911458333 or simply 8330 - (8330-3080)/4