Hey guys, I've been given a worksheet with a couple of questions concerning radioactivity, half-life etc. It is high school level and for me, it seems like the first year doing physics as our current teacher is the first one who really knows something about the subject. :) So please be patient with me. :) 1. The problem statement, all variables and given/known data "Consider having one kilogram of radioactive nitrogen 13 isotope – half-life is 10 minutes. How much nitrogen will you have after 30 minutes? When is the ratio between radioactive and non-radioactive material 1:31? Estimate when the ratio is 1:10." So, m0 = 1 kilogram mt (final mass) = x t = 30 minutes tHL (half-life) = 10 minutes 2. Relevant equations mt = m0/2^x 3. The attempt at a solution mt = 1/2^3 = 0.125 kg (since 3 H-Ls have occurred in the 30mins.) But that is everything I got to. I'm completely lost with the ratios. Could you help me, please? Next problem: 1. The problem statement, all variables and given/known data "How many times do you have to cut your fingernail in half to separate atoms from each other? How many times to get to atom’s nucleus? (suppose the fingernail is 0.5 cm long) 2. Relevant equations Well, as far as I know, the size of an atom should be equal to 10^-10 m while the size of a nucleus is 10^-14 m. 3. The attempt at a solution I think I need to convert the fingernail's size to a negative power so that it is easier to compute the quotient. So, 0.5 cm = 0.005 m = 5x10^-3 m. And I'm done.. :/ Could someone please explain the process in detail? Thanks so much!