Asample of fluorine-18 in a laboratory has an initial mass of 50mg. flourine-18 has a half life of 1.8 hours calculate the amount of time it will take for the initial mass of fluorine-18 to be reduced from 59 mg to 12.5mg

Total solidification times of three casting geometries are to be compared: a sphere, a cylinder, in which the length-to-diameter ration - 1.0, and a cube. volume = 1000 cm^3 for all three shhapes, and the same casting alloy is used. a) determine the solidification times of each geometry b) based on the results of part (a), which geometric element would make the best riser? c) if the mold constant = 3.5 min/cm^2 in chvorinov's rule, compute the total solidification time for each casting.

One form of energy can be another type of energy. a. created to form b. transformed into c. destroyed and then created to form

Idon’t know the answer to it and am stuck.