homework and exercises - 7 Billion people jumping at once

What would happen if every person in the world gathered at a minimum possible area and jumped all at once? Would that have any effect on Earth?

Answer

First, obligatory note: this was already answered by Randall Munroe of XKCD fame in his "What if blog" (this was his 8th question & answer posted).

The answer, as given by Randall (emphasis mine)

it doesn’t really affect the planet. Earth outweighs us by a factor of over ten trillion. On average, we humans can vertically jump maybe half a meter on a good day. Even if the Earth were rigid and responded instantly, it would be pushed down by less than an atom’s width

The problem is the 7 billion-ish people leaving said area.