7. Cobalt-60 has many medical applications. If the half-life of cobalt-60 is 5.25 years, how long after a new sample is arrived, its amount reduces to one-third of its original amount? The material loses what percent of its energy through this decay?

5. Krypton-85 is an inert radioactive noble gas with a half-life of approximately 10.76 years. a. Write an exponential function to model this situation and define each variable. ( b. Determine what fraction of a sample of Krypton-85 will remain after 86.08 years. State the answer as an exact fraction value. ( C. Determine how long will it take for a sample of Krypton-85 to decay to 1/64 of its original mass. Round your answer to the nearest hundredth of a year.

5. Krypton-85 is an inert radioactive noble gas with a half-life of approximately 10.76 years. a. Write an exponential function to model this situation and define each variable. ( b. Determine what fraction of a sample of Krypton-85 will remain after 86.08 years. State the answer as an exact fraction value. ( C. Determine how long will it take for a sample of Krypton-85 to decay to 1/64 of its original mass. Round your answer to the nearest hundredth of a year.

12. The half-life of Calcium-47 is 3.91 x 105 seconds. A sample contains 4.11 x 1016 nuclei. How much of the sample is left after 7.82 x 105 seconds? 2.57 x 1015 nuclei 5.14 x 1015 nuclei 2.06 x 1016 nuclei 1.03 x 1016 nuclei

11. A 60 kg person accidentally ingests a small source of alpha particles (RBE=15). The activity of the source is 0.04 Ci, the half life of the source is 110 years, and each alpha particle emitted has an energy of 0.586MEV. It takes 12 hours for the alpha source to pass through the persons digestive system and exit the body. (a) How many alpha particles are absorbed by the person (you may assume that 100% of the alpha particles emitted by the source are absorbed by the person)? (b) How much energy is deposited in the person by the source (in J)? (c) What is the absorbed dose (in rad)? (d) What is the absorbed dose (in rem)?

48. The mass of a nucleus of plutonium (Pu23994) is 238.990396 u. Show that the binding energy per nucleon for plutonium is 7.6 MeV (show your work on scratch papers). A radioactive isotope of an element decays with half-life 10 minutes. If originally there are 64 atoms in a sample of the element, what is the time that should pass until only one atom of the element is left out? What is the decay constant k?

15. An important tool in archeological research is radiocarbon dating, developed by the American chemist Willard F. Libby. This is a means of determining the age of certain wood and plant remains, hence of animal or human bones or artifacts found buried at the same levels. Radiocarbon dating is based on the fact that some wood or plant remains contain residual amounts of carbon-14, a radioactive isotope of carbon. This isotope is accumulated during the lifetime of the plant and begins to decay at its death. Since the half-life of carbon-14 is long (approximately 5,730 years¹), measurable amounts of carbon-14 remain after many thousands of years. If even a tiny fraction of the original amount of carbon-14 is still present, then by appropriate laboratory measurements the proportion of the original amount of carbon-14 that remains can be accurately determined. In other words, if Q(t) is the amount of carbon-14 at time t and Qo is the original amount, then the ratio Q(t)/Qo can be…

4. I have two isotopes A and A' of an element with half-lives T/2 and Ti2 respectively. (a) Show that with time, the amount of A' relative to A is NA (t) f (t) = NA (t) = f (0) exp In (2) ( (b) The half-lives of 238U and 235U are 4.5 billion years and 700 million years, respectively. Natural uranium is currently about 97.3% 238U and 0.7% 235U. Based on the formula in (a), how long ago would you have been able to build an atomic bomb out of natural uranium ore, given that "weapons grade" uranium is at least 80% 235U? [MY]

4. What is the energy released/absorbed in this nuclear reaction 4N+H³C + 3He? (The atomic mass of 14 Nis 14.003074 u, and that of 1³C is 13.003355 u) MeV

The curve to the right shows the radioactive decay of a particular sample of a nucleus called Element 9. A particular nucleus survives for the first 10 hours, what is the probability that particular nucleus of Element 9 will decay between 10 hours and 20 hours? N 400 - a. 50.0%. b. 75.0%. 100- c. 25.0%. d. above 98%. 5 10 15 t (in hrs) e. 86.5%.