How can the mass of an object be determined in a laboratory? the object is weighed. the dimensions of the object are measured. the object is balanced against standard units of mass. the object is balanced against standard weights. the volume of water which the object displaces is measured.

Ihave no idea how to solve these. plus there's another question that is 2) a 10 kilogram meteorite is collected in space and brought back to earth. it is composed of 1.25 kg of uranium-238 and 8.75 kg of lead-206. how many u-238 half lives have passed? what is the approximate age of the meteorite?