If a rock weights 5kg and is placed in water (fish tank) is that rock the same weight or lighter, why and how

Question

If a rock weights 5kg and is placed in water (fish tank) is that rock the same weight or lighter, why and how

Answer 1

The rock itself will have the same weight, but if it is porous, as many rocks are, it will absorb water into microscopic cavities all along its surface, actually making it weigh more.  Of course, at this point, it isn't the rock you're weighing, but the combined weight of the rock and the water inside it.

Answer 2

It is like saying put a brick in a aquarium how heavy is the brick? The brick is the same weight though the combined aquarium is increased due to the brick.

So it isn't the same or lighter, but additional weight.

("'\(o.o)/"')

Answer 3

The weight of the rock in water will be 5kg minus the weight of displaced water (with the same volumne of the roack).  This is according to the Archimedes' principle

Answer 4

Because of the Earth's gravitational pull, it's basically the same weight.  But, buoyant of the density of water vs. the density of the rock, it's just more buoyant.  To answer your question, it is if you weigh it in air and then weigh it in water, you will get that it is lighter when it is in water, but if you look at it in a universal view and factor in Earth’s gravitational pull, you will find out that, it’s all politics. :)

Answer 5

Well it still has the same mass, but the weigh may differ.  As to why, many types of rocks typically have small air bubbles in them and air being less dense then water would tend to float and offset some of the rocks weight.  In fact, weighing something in air and then in water can be used to determine the items density and typically they aren't identical.

Answer 6

its the same weight. it just displaces the water.