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contents:
Engl
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 2.2.2.
Calculation of
a linear momentum of the closed mechanical system of bodies in absolute
coordinates system for the working periodLinear momentum of all material system represented in a Fig. 1: 
Here:
Having stopped in a point
As is known, the geometrical point, radius-vector r which refers to as the center of mass of material system is defined by equality
As for the working period to a body
where
After substitution
let's receive:
Projections of speeds to corresponding axes of coordinates:
or, after simplification:
In a projection to axes of coordinates
system XOY a
linear momentum
According to a principle of conservation of momentum of the closed system:
The decision of the given system of the
differential equations concerning coordinates
yields following results:
, where:
In a Fig. 4 the plot of change of coordinates
is presented
Fig. 4 Once again we shall remind, that
values
With coordinate
Moving of the center of mass of all system of bodies looks like (Fig. 5):
Fig. 5
Dependence of moving of the center of mass of all closed system are presented in a Fig. 6 and a Fig. 7. Fig. 6 Fig. 7 Two plots presented on Fig.4 and Fig 5, collected in one plot:
Red color designates a trajectory
of
Conclusions. At observance condition of preservation of a momentum the given system ( Fig. 1) moves for the certain time interval on the certain distance ( Fig. 5).
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2.
- a linear momentum of all closed system consisting of a body 
and systems of mobile elements a lump
- speed of the center of mass of a body
.
,
these elements get speed of a body
-a linear momentum of system of mobile elements. Projections
and
coordinates of the center of mass of a body
and
,
and
(coordinates of the center of mass of the case), in view
of entry conditions:
Euler's constant:
Cosine integral:
Sine integral:
and
coordinates of the center of mass of all closed mechanical system
in coordinates system XOY.
and
it is possible to find as follows:
