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The gravitational forces between the Sun and planets provide the centirpetal forces to the planets, because of which they orbit around the Sun.
The momentum is the product of mass and velocity of the body. Angular momentum is the moment of the momentum, i.e., (r x mv). This is the vector product of the radius vector(joining the body and the revolution axis) to the momentum of the body.
The constant angular momentum (law of conservation of angular momentum is applicable) of the ...