Gravitation

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Question : 15
Total: 25
A body weighs 63 N on the surface of the earth. What is the gravitational force on it due to the earth at a height equal to half the radius of the earth?
Solution:  
Acceleration due to gravity g at height h is given by
g′=
gR2
(R+h)2

=
gR2
(R+R∕2)2

=
4
9
g

Gravitational force on body at height h is
F=mg′
=m
4
9
g

=mg
4
9

=63×
4
9
=28N[∵mg=63]
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