- #1
Ahmed Abdullah
- 203
- 3
I can't convince myself that I understand the mechanism of capillarity.
Say the liquid is of that type that rises through a capillary tube. So it's contact angle should be an acute angle.
Liquid molecules on the surface (in contact of gas) exert a force on the wall (of capilary tube) due to surface tension. According to Newtons third law the wall also exert an equal and opposite force on the molecules in contact. These molecules are also attracted by a same force by their neibouring molecules. These two force should cancel each other, if so then we should not observe the rise...
the book on the table feels a reaction force upward due to its weight, but it does not rises up. Same idea. The molecules in contact with the wall are constantly under the force, it is exerting on the wall. The wall only does something to make things steady. But why there is a rise?
I am sure I am missing something or i have some fundamental misconceptions about the source of surface tension...
Say the liquid is of that type that rises through a capillary tube. So it's contact angle should be an acute angle.
Liquid molecules on the surface (in contact of gas) exert a force on the wall (of capilary tube) due to surface tension. According to Newtons third law the wall also exert an equal and opposite force on the molecules in contact. These molecules are also attracted by a same force by their neibouring molecules. These two force should cancel each other, if so then we should not observe the rise...
the book on the table feels a reaction force upward due to its weight, but it does not rises up. Same idea. The molecules in contact with the wall are constantly under the force, it is exerting on the wall. The wall only does something to make things steady. But why there is a rise?
I am sure I am missing something or i have some fundamental misconceptions about the source of surface tension...