As dancers twirl faster and faster around their partners, they are demonstrating what type of energy? A. Binding energy,
B. Nuclear energy,
C. Kinetic energy,

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.)