SOLUTION: the half-life of the radioactive element unobtanium-47 is 5 seconds. If 80 grams of this are initially present, how many grams are present after 5 seconds?

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Question 466186: the half-life of the radioactive element unobtanium-47 is 5 seconds. If 80 grams of this are initially present, how many grams are present after 5 seconds?
Answer by richard1234(7193) About Me  (Show Source):
You can put this solution on YOUR website!
40 grams (after five seconds, one half-life has elapsed).

Fortunately, the half-life of unobtanium is longer than 5 seconds. Otherwise, Avatar's Hallelujah Mountains would become lose its magnetic fields (as unobtanium is theoretically a superconductor) and crash to the ground.