The half-life of cobalt-60 is 5.3 years. If you have a sample that contains 10.0 g of the isotope, how much will be left after 21.2 years?
A. 1.25 g
B. 0.625 g
C. 5.0 g
D. 2.5 g

You have been hired to design a spring-launched roller coaster thatwill carry two passengers per car. the car goes up a 10-m highhill, then descends 15m to the track's lowest point. you'vedetermined that the spring can be compressed a maximum o 2.0m andthat a loaded car will have a maximum mass of 400kg. for safetyreasons, the spring constant should be 10% larger than the minimumneeded for the car to just make it over the top. a) what spring constant (k) should you specify ? b) what is the maximum speed of a 350 kg car if the spring iscompressed the full amount.