Hydrostatics

What do you think Hydro-statics is ?

It is the static nature of bodies in liquids. This includes other liquids in liquid. That is to say that when something is in a liquid and it stays in the same place, it is static and from that section we remember that a body is only stationary if all the forces on the body are balanced.

So when are bodies stationary in water?

  1. When they sink
  2. When they float

We don't need to worry about the first its just like a body resting on a table, so don't forget there must be a resultant force from the bottom of the pool, but think, does the body fall through the water at the same speed as it would through air? Why not? Why does the force of gravity not pull the body through water as well as it does through air ? What effect does this have on the resultant ?

the second,

Why do objects float or sink? What decided this ?

Do objects sit on the surface of water ?

Some objects actually do .... here for more

how high does a body float ?

This, you should know, is density.

The amount of mass in a set volume of matter is the density.

Usually Chemists talk about g/cm3 but Physicists deal in kg/m3.

So you need to be able to convert from one to the other,

Notice both units have a volume with them, 1ml 1/1000 litre and 1 cubic meter, thats a cube with sides 1m x 1m x 1m.

Can u represent 1 cubic meter?

Q How many cubic centimeters are in a cubic meter ??

A A cubic meter is 1m x 1m x 1m, that is the same as 100cm x 100cm x 100cm

So what is the answer ?

So if each cm3 had a mass of 1 gram, how much mass would be in the cubic meter ?

In kilograms (kg) ??

So if the density of water is 1 g/cm3 what is that in kg/m3 ?

If the density of mercury is 13600 kg/m3 what is that in g/cm3 ?