I went to an excellent cookery demonstration last night. It was said that the way you tell the difference between apples and pears is that apples float and pears sink. The Internet agrees. This picture shows what I found in my kitchen. The pear is a sweet desert pear. We are wondering if it is a cross with an apple. It is also quite ripe so maybe that makes a difference. Further research is required. Internet answers say that apples continue to "breathe in oxygen". That doesn't sound scientific to me. For a start, breathe is a word used for mechanical ventilation by lungs. Plants absorb gases by diffusion. Perhaps apples do continue to do respiration, for which oxygen would be needed. I will try to find an answer. But respiration would create carbon dioxide gas which would pass out by diffusion. I'm not convinced that the apple ends up pumped with oxygen but I'll try to find a definitive answer.
Things float in water if they are less dense than water. The pear is almost under water so it must be very close to 1 gram per cubic centimetre. The apple sits higher in the water.
Archimedes says upthrust = weight of water displaced. Since the volume of water displaced is almost equal to the volume of the pear, density is almost water. Upthrust has to equal 0.098kg x g.
Upthrust = 0.129kg x g but say 10% of the apple is above the water. Then perhaps the density is 0.9 grams per cubic centimetre.
