1. a. Would you float more easily (ie. with less of your body immersed) in water
ID: 479885 • Letter: 1
Question
1. a. Would you float more easily (ie. with less of your body immersed) in water on the moon than on earth? Explain your answer fully b. A glass beaker, filled to the brim with water, is resting on a scale. A block is placed in the water, causing some of it to spill over. The water that spills is wiped away; the beaker is still filled to the brim. Explain fully how and why the initial and final readings on the scale compare if the block is made of. wood iron c. You have two identical drinking glasses. One contains free-floating ice cubes, and the other contains no ice. You fill each glass completely to the brim with water. Which glass now weighs more? Explain your answer.Explanation / Answer
(1)
(a) The level of immersion of our body in water would be the same on moon as on earth. Because this level depends on the bouyant force that needs to be applied upwards on our body, which in turn depends on our weight.
On moon, even though our weight decreases, the bouyant force needed to balance our "reduced weight" also decreases by the same proportion, and the level of immersion remains exactly the same.
(b)
The scale gives the same initial and final readings for both wood and iron. This is because even though a block is inserted, water also gets spilled out. The weight of water that spills out equals the weight of block inserted.
(c)
Both weigh the same, and the logic is exactly same as in part (b).
(2)
Volume of one log = pi*(35/2)2*975 = 938060 cm3
Total volume of raft = 14 * 938060 = 13132840 cm3
Density = 0.76 g/cm3
Mass of one log = 0.76*938060 = 712925.6 g = 712.93 kg
Total mass of raft = 14*712.93 = 9981 kg
When fully immersed such that the top surface is just slightly above water surface, the volume of water displaced by the raft = volume of raft itself = 131320 cm3
Mass of water displaced = 13132840 * 1 = 13132840 g = 13132.84 kg
Now,
Mass of water displaced = Mass of raft + Mass of persons
So, mass of persons = 13132.84 - 9981 = 3151.84 kg
No. of persons = Total mass of persons / Mass per person = 3151.84/75 = 42 persons
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