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2
a t 
h  .
2
Therefore
2h
a  .
t 2

As
a
 ,
R
we obtain
2 h
 .
t 2 R
Substituting equations we get a computation formula for determination
of unknow moment of inertia :

 gt 2 

 mRI 2  1 /
 2h 
 

7.FLUID DYNAMICS

Fluid dynamics is the study of fluids in motion. It is one of the
most complex branches of mechanics, which can be illustrated by such
familiar examples of fluid flow as a river in flood or a swirling cloud of

cigarette smoke. While each drop of water or each smoke particle is
governed by Newton's laws of motion, the resulting equations can be
exceedingly complex. Fortunately, many situations of practical

importance can be represented by idealized models that are simple
enough to permit detailed analysis.

7.1 Ideal fluid . Streamline. Flow Tube

Ideal fluid, is model of real liquid, i.e incompressible and
without internal friction or viscosity. The assumption of

incompressibility is usually a good approximation for liquids. A gas can
also be treated as incompressible if the pressure differences are not too
great. Internal friction in a fluid gives rise to shear stresses when two

adjacent layers of fluid move relative to each other, or when the fluid
flows inside a tube or around an obstacle. In some cases these shear
forces can be neglected in comparison with gravitational forces and

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