3. A radioactive isotope has a half-life of 17days. If a chemist has a sample of 200g, howlong will it take until there is 25g of the sample? Also calculate the activity of the radioisotope at this point (note that activity A = Nλ).​

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Ke reqd to move from 0 to 50 will be proportional to 50x50 or 2500. this is equal to w.  to change vel from 50 to 150 you need energy prop to 22500 - 2500 = 20,000. this corresponds to 8w.  best answer is a) . work reqd is prop to velocity squared.