Final answer:
The vertical dimension of the wood block above the water's surface is 0.72 cm. This is derived from considering the density of the wood and freshwater, and applying Archimedes' Principle. Since the wood floats, it doesn't sink to the bottom, and calculating a final velocity or time to reach the bottom is not relevant.
Step-by-step explanation:
The student's question involves calculating the vertical dimension at which a block of wood floats, the final velocity of the block, the buoyant force acting on the block, and determining the time the block takes to reach the lake bottom. However, some aspects of the question, such as the final velocity and the time to reach the lake bottom, are irrelevant if the wood is floating. When the wood is floating, it will not sink to the bottom and therefore does not have a 'final' velocity in the sense implied by the question.
Since the density of wood (0.7 g/ml) is less than that of freshwater (1.0 g/ml), the wood will float. According to Archimedes' Principle, the buoyant force equals the weight of the displaced fluid. The block displaces an amount of water equal to its own volume when fully submerged. The cross-sectional area is given as 11.2 cm x 13.5 cm, with a height of 2.4 cm, so the volume of the block is 362.88 cm³. However, since the wood's density is only 70% that of water, only 70% of the block would need to be submerged to displace a volume of water equal to the weight of the wood. Therefore, the vertical dimension of the wood above the water will be 30% of its total height, which is 0.3 x 2.4 cm = 0.72 cm.