What is the density and factors affecting sinking and floating?

Answer 1

Buoyancy. This is the force exerted by a fluid on an object. It is due to pressure difference in the fluid (pressure increases a you get deeper). Thus the force always acts in the opposite direction to gravity (upward).

The buoyancy force is equal to the WEIGHT of the fluid displaced by the object. Remember that weight is the FORCE due to gravity, and so buoyant force can vary if gravity varies.

The formula for calculating buoyant force is:

F = ρgV

where ρ is density of fluid and V is volume of fluid displaced.

Notice that ρ (density) times V (volume) is mass, and that mass times g (acceleration of gravity) is weight.

Also for your consideration...

An object will rise if buoyant force exceeds weight, like a balloon full of helium (gases like air are also fluids). If weight exceeds buoyancy, the object will sink, like a stone in water.

Weight can also be calculated like buoyancy:

W = ρgV

ρ is density of the object and V is volume of object.

So determining whether an object in a fluid will sink or rise can involve comparing density of fluid with average (bulk) density of object.

If the object is a solid object with known density you can detarmine if object will float our not. If density of object is greater than density of fluid it will sink, and vice versa.