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1. KINEMATICS OF MATERIAL POINT

1.1. Frame of Reference

To determine of the location of a body in the space at any time
it is necessary to choose frame of reference.
Frame of reference is usually understood as body of reference,

system of axes closely connected with it and clock (time device).
Body of reference is a body referring to which positions of other
objects are determined. Any body
can be chosen as the body of

reference. For example the Earth
can be the body of reference, where
system of coordinates (system of
а axes) are parallels-meridians system

(fig.1.1 a)
The meridian through

Greenwich, England (fig.1.1b), also
called the Prime Meridian, was set
at zero degrees of longitude, with

b other meridians being defined by
the angle at the centre of the Earth
between where it and the Prime
Meridian cross the equator. As there

are 360 degrees in a circle, the
meridian on the opposite side of the
Earth from Greenwich, forming the

other half of a circle with the one
through Greenwich, is 180°
longitude, and the others lie

c between 0° and 180° of West
longitude in the Western
Figure 1.1
Hemisphere (West of Greenwich)
and between 0° and 180° of East
longitude in the Eastern
Hemisphere (East of Greenwich). Most maps show the lines of
longitude. So, if you are in Greenwich you can be at the very same time

in Western Hemisphere and Eastern Hemisphere as shown in fig.1.1 c.

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