Question

Plutonium-238 is a radioactive isotope of plutonium that was often used as the power supply in cardiac pacemakers. One gram of Pu-238 generates approximately 0.5 watts of power. Suppose that 2 grams of the isotope were inserted into the pacemaker battery as a sealed source in the patient to provide power to the pacemaker. The rate at which Pu-238 decays can be modeled as

r(x) = −0.0158(0.992127535^x) grams per year

where t is the number of years since the 2 grams began decaying.†

(a) A pacemaker battery should last at least 5 years. How much of the Pu-238 will decay during the first five years? (Round your answer to three decimal places.)
  grams

How much power is generated by the amount remaining after 5 years? (Round your answer to three decimal places.)
watts

(b) How much of the Pu-238 will eventually decay? (Round your answer to three decimal places.)
  grams

Answer 1