concept of bouyancy for question 1...
when the rock was in the boat, a mass of water equal to the mass of the rock had to be be displaced in order for the rock to stay afloat. lets ignore the mass of man and boat because these 2 are constant.
but because water is less dense than the rock, more water (volumetric) has to be displaced than the volume of the rock. thus when the rock is dropped into the water, the only volume it takes up is its own...
thus, the answer is the water level will drop.
when the rock was in the boat, a mass of water equal to the mass of the rock had to be be displaced in order for the rock to stay afloat. lets ignore the mass of man and boat because these 2 are constant.
but because water is less dense than the rock, more water (volumetric) has to be displaced than the volume of the rock. thus when the rock is dropped into the water, the only volume it takes up is its own...
thus, the answer is the water level will drop.