A boat full with pieces of heavy rock is floating on the surface of water in a pool. When the pieces are throw

Question

A boat full with pieces of heavy rock is floating on the surface of water in a pool. When the pieces are thrown into water, what would happen with the level of water in the pool? Give the arguments in support of your point of view.

Answer 1

The level of the water will decrease.

While in the boat the rock is displacing volume of water equal to the WEIGHT of the rock.
If you throw then in the lake they will displace volume of water equal to the VOLUME of the rocks.

Assuming the the rock has higher density than water they will displace less water in the lake than in the boat. Thus the water level will decrease.

Answer 2

There are two ways to come to a solution :

1. Imagine the extreme case with 1 rock that's very small but _very_ dense. (Neutron star material, for example.) Keeping in mind Archimes' Law, and the difference between mass and volume, what would happen?

2. Find a teachers' website.

"In this featured brainteaser, when the 10-pound rock is in the boat, it is floating, so, in addition to what the boat would displace without the rock, it also displaces the amount of water with a weight equal to the rock. When the stone is hurled in the air -- so that it is out of the boat but not yet in the water -- the boat is relieved of the rock's weight and displaces less water. Consequently, the water level in the pool drops. When the rock enters the water, it displaces a volume of water equal to its size. Because the same volume of water weighs less (perhaps only 3 pounds) than the same volume of rock (10 pounds), the denser rock sinks to the bottom. The water level rises again, but not as high as it was when the rock was in the boat because it is now displacing less water. The net effect of throwing the rock in the pool, then, is a lowering of the water level."

"Buoyancy Brainteasers: Boat-in-Pool Puzzler" : http://www.teachersdomain.org/resources/phy03/sci/phys/matter/buopool/index.html

Answer 3

I'm guessing the water will lower in the pool because the boat was displacing the rock ,its self and the air in the boat. gravity and air pressure are also pulling,pushing at the rock which also displaced some volume of air in the boat.- with the rocks in the water-- the rocks and boat still displace water but not as much air volume because gravity isn't pulling(air pressure pushing) on the rocks in the boat. i don't think its as much about the rocks being denser than water--you could use plastic bags of water and id bet you get the same results--think its more to do with the atmospheric pressure above the water and gravity.

Answer 4

if the rock sinks, the water level will drop because of TWO reasons.

1) the weight of the rock is greater than its volume, so the sunk rock is not displacing as much as its weight was in the boat.

2)the boat will rise higher in the water since it has lost weight, and will displace less so the water level in the pool will drop because of that as well.

Answer 5

Nothing

The total displacement of the water in the lake is the same whether the rock is in the boat or in the lake.

Answer 6

the level of water would remain the same because initially as the water is displaced by the combined weightof boat and stones but when stones are removed the water level ofcourse rise but when the stones are dropped in water it would reach to the same level.

Answer 7

Ohhhhhhhhhhhhhhhhhhhhh, so much easyyyyyyyy,

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