“Big” * G* is Newton’s gravitational constant and gives the constant of proportionality in Newton’s Universal law of gravitation which is the basis of our understanding of non-relativistic gravity. The gravitational force

In SI units, * G* has the value 6.67 × 10

The direction of the force is in a straight line between the two bodies and is attractive.

Thus, an apple falls from a tree because it feels the gravitational force of the Earth and is therefore subject to “gravity”. The acceleration * g=F/m_{1}* due to gravity on the Earth can be calculated by substituting the mass and radii of the Earth into the above equation and hence

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