Whether it be from a tech giant or a small startup, engineering brain teasers are somewhat regularly asked in interviews. A common one is shown and answered below!
Question: A boat with a heavy rock on board is floating on a lake. If the rock goes overboard and it sinks to the bottom, did the water level rise, fall, or remain the same?
Answer: The root of this question is in fluidics! It comes down to the fact that the boat floats with the rock on it, but the rock then sinks when thrown overboard. This tells us that the volume of water displaced when the rock is on the boat is larger than when it has sunk to the bottom and therefore, the water level will counterintuitively fall! On the buoyant boat, the rock was displacing a volume of water driven by its weight, but in the water the denser rock was only displacing a volume of water driven by its volume. So long as the density of the rock is greater than the density of water, the water level will fall. Look up Archimedes’ principle to learn more!
