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Question
What is the direction of areal velocity of the earth around the sun?
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Solution
Areal velocity of the earth around the sun is given by `(dA)/(dt) = L/(2m)` where L is the angular momentum and m is the mass of the earth.
But angular momentum `L = r xx p = r xx mv`
∴ Areal velocity `((dA)/(dt)) = 1/(2m) (r xx mv) = 1/2 (r xx v)`
Therefore, the direction of areal velocity `((dA)/(dt))` is the direction of `(r xx v)`, i.e., perpendicular to the plane containing r and v and directed as given by the right-hand rule.
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