# Surface pressure

1. May 3, 2009

### kasse

I understand the explanation of tios problem, except the fact that the force acting upwards bacause of surface pressure is $$2 \pi r \gamma_{WG} cos(180 - \theta)$$. Why is that?

2. May 3, 2009

### Staff: Mentor

There is the bouyancy force and the surface tension. The water pressure acts normal to the surface, but surface tension acts tangentially. Weight of course acts downward with gravity, and to balance the forces, on is concerned with the components of pressure and surface tension acting vertically.

3. Apr 13, 2011

### yohan75

A steel blade placed gently on the surface of water floats on it. If the same blade is kept well inside the water it sinks. Can you people please explain why? Thanks for the lot of info that you post. It is really of great help.