A block of Styrofoam floats on water while a lead block of the same size block lies submerged in the water. The buoyant force is greatest on the
A)lead.
B)Styrofoam.
C)same for both

Question

Quizplus · Accepted Answer

The buoyant force on an object is equal to the weight of the fluid displaced by the object. Since both blocks are of the same size, they displace the same volume of water. However, the lead block, being denser, will be fully submerged to displace that volume, while the Styrofoam block, being less dense, will only be partially submerged. Despite this, the volume of water displaced (and thus the buoyant force) is determined when the object is fully submerged. Therefore, the buoyant force must be enough to support the entire weight of the lead block underwater, making it greater for the lead block than for the partially submerged Styrofoam block.

A Block of Styrofoam Floats on Water While a Lead