Why does water stay indide a straw when i cover the top?

Question

Why does water stay indide a straw when i cover the top?

Answer 1

Your finger creates a mini vacuum.  It's that simple.

Answer 2

pressure difference betweem top and bottom of straw.  

Sum forces, acting down to push water out of straw = weight of water plus (pressure acting on top of water column * area of column {straw}).  

Force acting up to keep water from running out of straw = pressure acting upward (atmosphere) * area of straw.

Set force up = force down, you get that the column of water will descend until the weight of the water left in the straw = area of straw * (upward pressure {atm} - downward pressure {partial vacuum on top of column because it moved down a little}).

Answer 3

Vacuum

Answer 4

when you covert he top it creates a vacuum and whatever is in the straw gets trapped and cant come out.

Answer 5

I just want my 2 points because other people actually answered it.

Answer 6

Funny: Because the water thinks your cover is the ground! Being up side down, couldn't make a straight decision.

Answer 7

Because pressure. If you cover the top if the water came down a vacuum keeps it there as no air can enter though the top.