VOA慢速英语:Eureka! A Word of Discovery

line – n. merchandise or services of the same general class for sale or regularly available

brand – n. a category of products that are all made by a particular company and all have a particular name

goldsmith – n. a person who makes gold jewelry and other gold items

volume – n. the amount of space occupied by a three-dimensional object as measured in cubic units (as quarts or liters) :

bulky – adj. having great volume in proportion to weight

prospector – n. someone who explores an area for natural resources

Law of buoyancy (Archimedes' principle) indicates that the upward buoyant force that is exerted on a body immersed in a fluid, whether fully or partially submerged, is equal to the weight of the fluid that the body displaces and it acts in the upward direction at the center of mass of the displaced fluid.

buoyancy – n. the tendency of a body to float or to rise when submerged in a fluid; the power of a fluid to exert an upward force on a body placed in it; also : the upward force exerted

breakthrough – n. a sudden increase in knowledge, understanding, etc. : an important discovery that happens after trying for a long time to understand or explain something