In Times Square in New York City, people celebrate on New Year's Eve. Some just stand around, but many move about randomly. Consider a system consisting of all these people. Approximately, what is the total linear momentum of this system at any given instant? Justify your answer.

Zero

Explanation:

The linear momentum these people at any instant is approximately zero. Because momentum is a vector quantity the random directions of their movement make their momentum in different directions and come back to their position which in ideal case makes it equal to zero.