Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Salamander on 08/04/2010 19:30:02

Title: How can I get liquid further up a straw?
Post by: Salamander on 08/04/2010 19:30:02

Jeff Thompson asked the Naked Scientists:
   
I am one of those easily amused persons who wants to understand the science behind everyday phenomena.  Lately, I've been experimenting with drinking straws and beverages in cups.

I hold the straw between my thumb and middle two fingers while closing the end with my index finger.  I then lower the straw in hte beverage to about 1/4" from the bottom of the cup and remove my index finger from the other end of the straw. The liquid will rapidly rise inside the straw to level of the liquid outside the straw, and then some.

I know that, eventually, the pressure inside and outside the straw will equalize and hte levels will be about the same, ignoring capillary action. But interia must be at work somehow, so I figure that the ratio of the cup diameter to that of the straw is one factor that determines the maximum height of the liquid in the straw shortly after opening top end.

What are the other major factors, and how can I get the rising liquid to overflow the straw?

What do you think?

Title: How can I get liquid further up a straw?
Post by: Soul Surfer on 08/04/2010 22:16:22

The length of the straw is also another fact. the longer the straw the more inertia is in the column and a very long pipe down into a deep lake can create a fountain

Title: How can I get liquid further up a straw?
Post by: Bored chemist on 09/04/2010 12:09:29

Can I just point out that inertia isn't the same as momentum?
A big bore pipe will lose less energy to friction /  viscosity than a narrow one. Also hot water is less viscous than cold water.