Sink or float (People got me wrong last time)?

Question

There is a cylinder which is 12 cm long placed in a beaker filled with water, the rim of the cylinder is 1cm above water level. The cylinder has some sand in it to stabilize it. Then, oil is added into THE CYLINDER (which contains the sand) and the specific density of oil is 0.8. The question is when the oil is added to the sand, will the cylinder float or sink????

Answer 1

The oil will displace the AIR in the cylinder. As oil weighs more/is more dense than air, I say that the cylinder will continue to sink like it did before.



However if you replaced some sand with oil then it depends on the density of the sand, the oil and also the cylinder.

Answer 2

You don't specify how much oil is added to the cylinder. If enough oil is added to the cylinder to make it's weight greater than the weight of water it can displace, it will sink. The cylinder with sand and air in it has a density of 0.917 g/ml, so it will take very little oil to bring it's density up to 1.0 g/ml. (Oil, though less dense than water, is much more dense than the air in the cylinder it is displacing.)

Answer 3

Simple answer is you can add oil column of height equal to the inverse of relative density.





If the cylinder immerses to a depth 1cm, the cylinder will sink.



Mass of water displaced in that case is A x 1cm x density of water.



The cylinder will just float if we add so much mass to the cylinder.



If oil is poured the volume of oil that can be poured into the cylinder is determined as follows.



The maximum mass of oil needed to add so that the cylinder floats is



A x 1cm x density of water



Volume of oil is = mass / density.



= {A x 1cm x density of water.} / {0.8 x density of water}



= A x1cm / 0.8



= 1.25 A x 1 cm.



Hence you can safely add oil up to a height of 1.25 cm.

Answer 4

sink. The density of the oil is less than the water, but the sand is denser than the water. Adding oil won't lower the density of the material inside the cylinder.

Answer 5

The only thing of importance is the weight of the cylinder and the weight of the water it replaces.

If the cylinder weighs less than the replaced water it will float, if more it will sink.