Engineering Board Exam Reviewer · Applications: Growth and Decay · medium

A radioactive isotope has a decay constant k=0.05 per year. Find its half-life.

  1. 13.86 yr
  2. 20.00 yr
  3. 6.93 yr
  4. 27.72 yr

Answer

A. 13.86 yr

Solution

t1/2= 2/k=0.6931/0.05 13.86 years.

More Applications: Growth and Decay questions

  1. Money is invested at a continuously compounded interest rate of 6% per year (dA/dt=rA). How long will it take for the investment to double?
  2. A population of bacteria starts at 500 and grows exponentially with k=0.3 per hour. Find the population after 4 hours.
  3. A radioactive substance initially has 80 grams and decays to 20 grams after 40 days. Find the decay constant k.
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  5. A population grows according to dP/dt=kP. If the population doubles in 10 years, find k.
  6. A radioactive substance decays according to dA/dt=-kA. If its half-life is 20 years, find k.
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