Question

A simple compass can be made by placing a small bar magnet on a cork floating in water. What fraction of a plain cork will be submerged when floating in water?

a) 1/2
b) 1/3
c) 1/4
d) 1/5

Answer 1

The fraction of a plain cork submerged in water is generally 1/4, considering cork typically has about one-fourth the density of water. Hence option (c) is correct.

Step-by-step explanation:

To find out what fraction of a plain cork would be submerged when floating in water, we apply the principle of buoyancy, which states that the buoyant force on an object in a fluid is equal to the weight of the fluid displaced by the object. Cork is less dense than water, and for the cork to float, the amount of water displaced must equal the weight of the cork.

For the cork alone, since it's floating and at equilibrium, the fraction of the cork submerged would be equal to the ratio of the density of the cork to the density of water. If the densities are equal, the cork would be completely submerged (1/1), but since the cork is less dense, the fraction is less than 1. It's common for cork to have about one-fourth the density of water, which would have it submerged by 1/4.