A 90 kg climber rappels from the top of a cliff with an acceleration of 1.0 m/s. Determine the tension in the climber's rope.

The radioactive isotope of lead, pb-209, decays at a rate proportional to the amount present at time t and has a half-life of 3.3 hours. if 1 gram of this isotope is present initially, how long will it take for 80% of the lead to decay? (round your answer to two decimal places.)