Question
In Exercises 14 -18, we list some radioactive isotopes and their associated half lives Assume that each decays according to the formula A(t) = A ekt where Ao is the initial amount of the material and k is the decay constant. For esch isotope: Find the decay constant k. Round your answer to four decimal places. Find a funetion which gives the amount of isotope A which remains after tme t. (Keep the units of A and t the same as the given data.) Determine how long it takes for 90% of the material to decay. Round your answer to two decimal places. (HINT: If 90% of the minterial decays, how much is left?) 18. Uranium 235, used for nuclear power, initial amount 1 kg grams, half-life 704 million years Book answers: 18. the ~-0.0010 % ~ 2302.58 million years, or 2.30 billion yors
Explanation / Answer
We have A = A0ekt, where A0 is the initial amount of the radioactive isotope and k is the constant of decay.
18.