i just want to know that if body moves from rest how its centre of mass remain zero after coming in motion?plz explain with more than 4 examples so that i can able to understand the applications of c.o.m. in physics for best preparation of iit jee 2011.

Dear shanky

if you are taking about a single rigid body then its center of mass will also move if the body moves.

 and if you are consederinf a system of more than two body then its center of mass may remain in rest provided that

  = m₁ V₁ + m₂V₂ + m₃V₃ + ....... m_nV_n = 0 

  where m1,m2,m3,m4   are the mass of different body  and V1,V2,V3 are their velocities repetively .

if m₁ V₁ + m₂V₂ + m₃V₃ + ....... m_nV_n ≠  0   then center of mass of the center will also move.

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