```Law of Flotation                                        Relative density or Specific Gravity
    It states that a floating object displaces its        It is the ratio of the density (mass of a unit
own weight of the fluid in which it floats.            volume) of a substance to the density of a
i.e.                                                   given reference material.
    Weight of floating object = weight of                 It is a dimensionless quantity, as it is the
fluid displaced                                        ratio of either densities or weights.
    Mass of floating object = mass of fluid                RD 
subst an ce
displaced                                                     reference
    Any changes in the density of the                     In SI units, the density of water is
surrounding liquid affects the level in                (approximately) 1000 kg/m3 or 1 g/cm3,
which an object floats.                                which makes relative density calculations
particularly convenient: the density of the
Density (ρ)                                                 object only needs to be divided by 1000 or
1, depending on the units.
    It is its mass per unit volume. The symbol
used for density is ρ.                             Viscosity (η)
m
    
V                                                It is a fluid"s resistance to flow.
    Where ρ is the density, m is the mass, and            Fluids become less viscous as the liquid"s
V is the volume.                                       temperature increases, becoming more
    Its unit is kilograms per cubic meter                  viscous as the fluid gets cooler.
(kg/m3).                                              A viscous fluid is sticky, thick and syrupy
    If we take a cubic centimeter of some                  to a greater or lesser extent.
commonly known substances, we can see                 Its unit is the pascal second (Pa s)
that they weigh different amounts:                    1 pascal second = 10 poise = 1,000
millipascal second
   1 centipoise = 1 millipascal second
   e.g. Treacle is quite viscous, but water is
not. Hot engine oil is less viscous
("thinner") and runs more quickly and
smoothly than cold engine oil.
Bernoulli"s Principle
So from the above examples it is easy to see
that some of the cubes weigh more than others,             It states that a rise (fall) in pressure in a
even though they all take up the same amount                flowing fluid must always be accompanied
of space.                                                   by a decrease (increase) in the speed, and
conversely, if an increase (decrease) in,
Entity                ρ (kg/m3)                the speed of the fluid results in a decrease
Interstellar medium                                         (increase) in the pressure.
* Assuming 90% H, 10%           1×10−19                    It states that Pressure energy + Kinetic
He; variable T                                              energy + Datum or Potential energy =
The Earth (Mean density)        5,515                       Constant
The Inner Core of the Earth     13,000                       v2          p
The core of the Sun             33,000–160,000                  gz   constant ,  where:
2           
Super-massive Black hole        9×105
   v is the fluid flow speed at a point on a
White dwarf star                2.1×109
Atomic nuclei                   2.3×1017
streamline,
Neutron star                    1×1018                     g is the acceleration due to gravity,
   z is the elevation of the point above a
Stellar-Mass Black hole         1×1018                      reference plane, with the positive z-
direction pointing upward – so in the
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