a 1.0m1.0m by 2.0m2.0m by 3.0m3.0m rectangular block has a uniform density of 600kg/m3600kg/m3and is completely submerged and held stationary in a deep pool of water. the water exerts an upward buoyant force on the block of 6×104n6×104n . the block is released and, after rising a short distance toward the surface, experiences a drag force of 2×104n2×104n. the magnitude of the acceleration of the block at this instant is most nearly