8th Grade Engineering Practice Exam

Buoyancy is the upward push a fluid gives to anything immersed in it. This force comes from fluid pressure, which increases with depth, so the pressure on the bottom of the object is greater than the pressure on the top. When these pressure forces are combined over the object's surface, they yield a net upward force. According to Archimedes' principle, the buoyant force equals the weight of the fluid displaced by the object. This explains why objects float if the buoyant force is greater than or equal to their weight, and sink if it is smaller. This upward force is different from drag (resistance to motion through the fluid), weight (gravity pulling downward), and pressure (force per area) because buoyancy specifically refers to the net upward effect caused by the fluid’s pressure distribution.