When a solid is dropped from the boat (floating in water)into the water ,then the level of water will fall if density of that solid body is greater than density of water i.e when that solid body sinks.WHY?I tried hard ,but i am unable to figured it out according to my calculation if solid object sinks it should displace less water so water level should not rise.another question is the water level will remain unchanged if density of that solid is less than density of water i.e when that solid body floats.WHY?PLEASE HELP .

Answer 1

The boat and its contents are floating, so its general density is less than that of water. So, the boat displaces a volume of water which has the same mass as the boat.

But a rock is denser, so it displaces less water.

SO, the amount of water displaced drops when the rock enters the water, because it displaces less water that its share of the weight did when it was in the boat.