Hang two sheets of paper vertically from adjacent corners. the sheets should be parallel and close to each other with a small gap between them. now gently blow down between the two sheets. what happens?

The sheets move toward each other and the gap narrows                      

Explanation:

          When two sheets are arranged or hanged in such a way, there is a small gap in between the two parallelly hanging sheets. This gap is filled by the surrounding air.

          Now if we blow gently in between the gap of the two sheets, we will observe that the two sheets move towards each other and will come closer thereby narrowing the gap in between them.  

          This is because as we blow through the gap, partial vacuum is created in between the sheet for a short time. So this vacuum is filled by the air surrounding the two sheets thereby forcing the two sheets closer.

it would be kevlar ^^

the part of the wave he is travelling on is the crest