Question

A boat carrying a number of large stones is floating in a water tank. What would happen to the water level, if the stones are unloaded into water?
A) Rises
B) Falls
C) Remains unchanged
D) Rises till half the number of stones are unloaded and then begins to fall

Answer 1

Hint: The solution to this question is rather easy and can be approached as by comparing the density of stones with the density of water, also, first you need to compare the density of the boat with that of water, to have an initial condition for the situation.

Complete step by step answer:
We will try to reach the solution to the question exactly like we told in the hint section of the solution.
First, we need to have an initial condition of the situation and we can have that by comparing the density of the boat with that of the water. We already know that boats float on the water surface because the density of the material using which the boat is built is lesser than that of water and thus it does not sink into the water body. Hence, at first, we can say that the boat and stones in it are floating on the water surface.
Now, the question has told us that the stones are unloaded into the water and asks us about what will happen. The point that should be noted is that the density of stones is quite high than the density of water, due to which, the stones will sink into the water and will replace the water of the exact same volume as the volume of the stones itself, this will cause a significant rise in the water level as its replaced volume will now need to compensate by increasing the water level to a new height.

Hence, The correct answer is Option (A).

Note: This question is quite easy and basic, students make mistakes in the fact that as long as the stones are in the boat, they are not replacing any volume of the water and are floating because only the density of the material of the boat decides whether they will float or not. Once, they are unloaded into the water, their own density will decide whether they will float or not, and they will sink in, along with causing a rise in the water level.