The radioactive element polonium decays according to the law given below where Q

Question

The radioactive element polonium decays according to the law given below where Q0 is the initial amount and the time t is measured in days.

Q(t) = Q0 · 2-(t/140)

If the amount of polonium left after 560 days is 90 mg, what was the initial amount present?

Strontium 90 (Sr-90), a radioactive isotope of strontium, is present in the fallout resulting from nuclear explosions. It is especially hazardous to animal life, including humans, because, upon ingestion of contaminated food, it is absorbed into the bone structure. Its half-life is 27 years. If the amount of Sr-90 in a certain area is found to be 16 times the "safe" level, find how much time must elapse before the safe level is reached.

g/cm3

Wood deposits recovered from an archaeological site contain 34% of the C-14 they originally contained. How long ago did the tree from which the wood was obtained die? (Assume the half life of carbon-14 is 5730 years. Round your answer to the nearest whole number.)
yr

The length (in centimeters) of a typical Pacific halibut t years old is approximately

Consider the function

where Q(t) is the size of a quantity at time t, and A, C, and k are positive constants. The graph of this function, called the Gompertz growth curve, is used by biologists to describe restricted population growth.

Explanation / Answer

i) given Q(t) = 2Q0 - (t/140) =

now given 560days the decay is 90mg

=> 2.Q0 - (560/140) = 90

= 2Q0 - 4 =90

=> Q0 = 11.25

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