A projectile moving under gravity explodes into several fragments in mid-air. Neglect air resistance. Which statement about the centre of mass is correct?
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A projectile moving under gravity explodes into several fragments in mid-air. Neglect air resistance. Which statement about the centre of mass is correct?

G1 Physics · Accepted Answer

The explosion produces only internal forces between fragments. Internal forces cannot change the motion of the centre of mass. The only external force on the complete collection of fragments is gravity, equal to the total mass times g. Therefore a(CM) = g downward both before and after the explosion. Hence the centre of mass continues on the same projectile path that the original body would have followed.