8. A block of wood with a density 7/10 that of water floats in water as shown in
ID: 1452673 • Letter: 8
Question
8. A block of wood with a density 7/10 that of water floats in water as shown in the figure. Paint thinner, with density 6/10 that of water and which does not mix with the water is added slowly until the block is completely covered by the paint thinner. This causes the block to ... (select one)
A)be pushed down more deeply into the water
B)remain in the same position
C) rise, with less of the block in the water
A block of wood with a density 7/10 that of water floats in water as shown in the figure. Paint thinner, with density 6/10 that of water and which does not mix with the water is added slowly until the block is completely covered by the paint thinner. This causes the block to (select one) be pushed down more déeply into the water. o remain in the same position rise, with less of the block in the water. sink to the bottom.Explanation / Answer
As per Archimedes' Principle, to float, the weight of the displaced water must be equal to the weight of the block (ignoring the displacement of the air by the non submerged part of the block, obviously).
The paint has a lower density than the wood. If it had a higher density than the wood, the wood would float on the paint, which would be unable to cover the block.
The mass of paint displaced by the part of the wood block above the water surface, contributes to the upward force supporting the block. This extra force means that the water has to provide a smaller contribution so the amount of water that is displaced by the block is less.
The volume of wood submerged in water will be less after the paint is added.
Thus answer is C) rise, with less of the block in the water.
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