HELP PLEASE ASAP Question 5 of 15 Lead-196 has a half-life of 37 minutes. It decays into thallium-196. Suppose a
sample contains 20 atoms of lead-196 and 60 atoms of thallium-196. About
how old is the sample?
A. 74 minutes
O B. 37 minutes
O c. 111 minutes
O D. 148 minutes

Engines for propeller-driven aircraft are limited in their maximum rotational speed by the fact that the tip speed of the propeller must not approach the speed of sound in air (mach i). taking 6 ft as a typical diameter for a propeller of a light airplane and 1100 fils as the speed of sound, find the upper limit on the rpm (revolutions per minute) of the propeller shaft.