According to physics, why does the stream of water flowing from a faucet get more narrow as the water falls?

Question

I think it has something to do with Bernoulli's principle, but if the pressure of the air is less than wouldn't the water spread out instead of in?

Answer 1

I would think it would be because of gravity. The water is unable to maintain the consistent shape it had when it exited the faucet because gravity was stretching it out as it fell.

Answer 2

I believe this is caused because as the water falls from the faucet gravity forces the water to fall at a faster pace the farther it falls. As it does this, the speed plus the force of the gravity pulling down creates more pressure further down which causes the water molecules to pack closer together.

Answer 3

This effect is due to the surface tension of the water molcules.

The water molecules in contact with air have the tendancy to decrease the total surface area of the liquid. This is due to the fact that the water molecules in contact with the air do not feel the same attractive forces from the air, resulting in a net force toward the center of the stream.

Answer 4

Cohesion will shape the cross-section of the water column into a circle. Water leaves a faucet with a constant mass flowrate, defined by ρAvwhere ρ is the density, A the cross-sectional area, and v the velocity. The velocity equation v^2 = v0^2 + 2as holds for the stream of water, so the velocity is increasing as the square root of the distance from the faucett. The mass flowrate must remain constant, so
ρA√(v0^2 + 2gs) = Q, and
A = πr^2 = Q/(ρ√(v0^2 + 2gs))
and the radius of the water column,
r = √(Q/(πρ√(v0^2 + 2gs))
r = √(πρr0^2v0/(πρ√(v0^2 + 2gs))
r = r0√(v0/√(v0^2 + 2gs)
r = r0√(1/√(1 + 2gs/v0^2)

Answer 5

when in the pipe it can spread..but when gravity pulls it downward it compacts because the surface of the pipe is gone.