Aradioactive isotope of potassium has a half-life of 20 minutes if a 40 g sample of this isotope is allowed to decay for 80 minutes how many grams of the r adioactive isotope will remain

The air that we breath is made mostly of which gaseous molecule

If you place a magnet under a clear dish, and sprinkle iron fillings over it, above what part of the magnet will most of the fillings gather

Four objects each with charge +2.0×10−7c are located at the corners of a square whose sides are 2.0 m long. part a what quantities can be determined using this information? check all that apply. the electric force on a charged object placed at the center of the square. the mass of each object. the total electric potential energy of the system consisting of the four charged objects. part b find the electric force on a charged object placed at the center of the square.