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The law of conservation of momentum states that there is no change in momentum in an isolated system.

(i)Total momentum = mass × velocity = 10⁸×60×4 = 2.4×10¹⁰kgm/s

(ii)According to the law of conservation of momentum, the earth will gain the same momentum in the opposite direction so that there is no change in the momentum of the system (total momentum remains zero).

So the recoil velocity of the Earth =

= 4 × 10^-15 m/s

This velocity is negligibly small. So there’s no observable effect.