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F
g  (4.5)
m test
According to Newton's law of Universal Gravitation

m  m test
F  G (4.6)
r 2
Substitute (4.5) in (4.6) and obtain formula of intensity g of

gravitational field of material point with mass m on arbitrary distance r.
m
g  G (4.9)
r 2

2..Gravitational ield of

spherical distribution of
matter.

Especially demonstrative
in this respect is

gravitational field of
Earth(fig.4.4).
If to consider our
planet- the Earth as
Figure 4.3
spherically symmetric
body with constant
density we can prove

that gravitational field
changes by linear law
from zero at the centre to
the maximum at the

Earth's surface
M
g  G r  (4.6)
R 3
where M - mass of the

Figure 4.3 Earth. R- its radius and
should take into account
that r  R.Outside the Earth its gravitational field is the same as

gravitational field of material point with mass M

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