Question

A stone of 1kg is at Earth's surface. Find the gravitational force between the stone and the earth.
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Answer 1

Answer:

F=Gm1m2/r^2

using G= 6.67*10^-11

m1=1kg

m2= 6*10^24kg

r=6.4 * 10^6 m

we get,

F= 10N

or, simply. F=mg= 1kg*10m/s^2= 10N

Explanation:

Earth attracts any body on it's surface with force equal to weight of the body(i.e. mg) . using formula one can consider Earth's mass concentrated at it's centre of mass ( which is here it's geometrical centre)