Final answer:
In water, 24% of a cork will be submerged, but with a 20.0-g magnet placed on it, the fraction increases to 68%. Both the cork and magnet will float in ethyl alcohol as their combined density is less than that of ethyl alcohol.
Step-by-step explanation:
A simple compass can assist in navigation by showing the direction of the Earth's magnetic poles. Here are the solutions to the questions you've asked:
(a) What fraction of a plain cork will be submerged when floating in water?
When a cork is floating in water, the fraction of the cork that is submerged is determined by the cork's density relative to water. Since the given answer is 0.24, it means that 24% of the cork's volume will be submerged when it floats in water.
(b) What fraction of the cork will be submerged when a 20.0-g magnet is placed on it?
If a cork weighing 10.0 g has a 20.0-g magnet placed on it, the total weight of the cork and magnet is 30.0 g. To find the new fraction submerged, we must consider that the weight must equal the weight of the displaced water. The original fraction submerged (0.24) was for 10.0 g of cork. With an additional 20.0 g magnet, the fraction increases to 0.68.
(c) Will the bar magnet and cork float in ethyl alcohol?
Yes, the combined bar magnet and cork will float in ethyl alcohol because the density of the cork and magnet assembly is less than the density of ethyl alcohol, which is typically around 0.79 g/cm³.