Two spheres are made of wood-the first is of a variety of wood whose density is equal to that of water, while the second is of a variety whose density is greater than that of water. These spheres have the same volume, and the first remains wherever it is placed in the water (so it is effectively suspended in mid-water). The second rests on the bottom, being more dense than water. Compare the buoyant forces on the two spheres.
A) Nothing specifically can be concluded without knowing exactly the densities of the spheres.
B) They are identical
C) The force on the second is zero, and therefore less than that on the first, which is non-zero.
D) The force on the second is non-zero and is less than that on the first.

Question

Quizplus · Accepted Answer

The buoyant force on an object submerged in a fluid is equal to the weight of the fluid displaced by the object. Since both spheres have the same volume and are fully submerged (one in the middle of the water and the other at the bottom), they displace the same amount of water and thus experience the same buoyant force, regardless of their densities.

Two Spheres Are Made of Wood-The First Is of a Variety