I was reading about COM and forces and came upon this in my book.
If a projectle explodes in air in different paths,the path of the centre of mass remains unchanged.This is because during explosion no external force (except gravity ) acts on the COM.
My question is, even though the author realises that there is gravity acting on the particle yet he goes on to conclude that the path of COM remains unchanged. But I learned that path will change whenever there is an external unbalanced force.Here gravity acts but why has the author neglected its effect ? (or am I mistaken somewhere?)