Question

Aunaun

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HN) Exercises
(1)You take 200 milligrams of a headache medicine, and after 4 hours, 120 milligrams remain
in your system. If the effects of the medicine wear off when less than 80 milligrams remain,
when will you need to take a second dose, assuming the anmount of medicine in your system
decays exponentially?
13 ส.ค.
The half-life of Radium-226 is 1590 years. If a sample initially contains 200 mg. how many
milligrams will remain after 1000 years?
)The half-life of Fermium-253 is 3 days. If a sample initially contains 100 mg, how many
milligrams will remain after 1 week?
บ้อ
The half-life of Erbium-165 is 10.4 hours. After 24 hours a sample still contains 2 mg. What
was the initial mass of the sample, and how much will remain after another 3 days?
The half-life of Nobelium-259 is 58 minutes. After 3 hours a sample still contains10 mg.
What was the initial mass of the sample, and how much will remain after another 8 hours?
(6) A scientist begins with 250 grams of a radioactive substance. After 225 minutes, the sample
has decayed to 32 grams. Find the half-life of this substance.
A wooden artifact from an archeological dig contains 60 percent of the carbon-14 that is
present in living trees. How long ago was the artifact made? (The half-life of carbon-14 is
5730 years.)