How can dropping a 2000kg stone into a small lake cause the water level to go down?

Question

there are 2 scenarios to answer this question
this was asked at cambridge medical interview so i know it already

Answer 1

in our area this could definitely happen.

Many small ponds here are constructed, rather than natural. The water is held in by a layer of clay that is intentionally added to seal the bottom. If the clay is disturbed, it can allow a substantial amount of water to leak out before it settles down again, or the whole pond may leak out. Dropping a huge rock into the pond could definitely break the clay seal.

In the western USA during various range wars, it was a common tactic to throw a stick of dynamite into a ranchers pond. The pond would drain out as described above, and then the cattle would have no water.

Answer 2

There are several ways, most have already been said more or less, but to clarify

1. The stone displaces a volume of water on impact greater than its own volume and does not change the shape of the lake. If the water taken out by the stone took up more space than the stone adds being in the lake then the level will go down.

2. The stone changes the shape of the lake, 2000kg is very heavy and so it's likely that this will happen. Any increase in depth caused by the stone will cause the water level to appear to decrease however, if the indent made by the stone is narrower than the river the lake will in fact be deeper. It is only if the stone is wider than the lake, and so makes the lake wider that the olake will become less deep, and the water level will actually go down.

3. The idea of the stone dammiing the lake is very nice, and true, if the stone blocks incoming water the water-level will go down over time.

Answer 3

easy

the stone cracked the bottom of the lake and revealed a under water cavern that filled and hence the water lvl droped

or

it was droped from a great height and displaced the water leaving less in there than there was

or

you might drop it at the mouth of the river feeding the lake, effectively daming it up and thusly the water will slowly evaporate.

Answer 4

It could create a very large hole making the depth of the lake larger so the water level would appear to lower.
If it was a very spongey stone it could soak up the water?
Also the rock would create a VERY large splash so the water would no longer be in the lake.

Answer 5

Firstly, the splash caused bu the rock in the water might displace more than the rocks mass of water.

Secondly, you might drop it at the mouth of the river feeding the lake, effectively daming it up and thusly the water will slowly evaporate.

Answer 6

you are talking about a stone that weighs roughly 2 tons so in a small lake i would say that the size of the stone would most likely displace the water in the lake......and at this weight i dont know so much that its a small stone as it is a large boulder

Answer 7

It might splash and send more water out of the lak than it displaces. Also, maybe it sinks deeply into the sediment and actually makes the lake deeper!!

Answer 8

1) cause the splash of dropping in it sends water out
2) the stone makes a causes a dent in the bottom that the water then feels in which makes the water level drop

Answer 9

It fell on the cambridge medical interviewer's head causing him to hallucinate?

Answer 10

1st "How" are you going to drop a 2000kg stone into the lake,

2ND, the water does not go down, the water is dispersed.