Q.

Water is filled up to a height h in a beaker of radius R as shown in the figure. The density of water is ρ, the surface tension of water is T and the atmospheric pressure is P0. Consider a vertical section ABCD of the water column through a diameter of the beaker. The force on water on one side of this section by water on the other side of this section has magnitude                             [2007]

1 |2P0Rh+πR2ρgh-2RT|  
2 |2P0Rh+Rρgh2-2RT|  
3 |P0πR2+Rρgh2-2RT|  
4 |P0πR2+Rρgh2+2RT|  

Ans.

(2)

In the first part the force is created due to pressure and in the second part the force is due to surface tension T.

The force is [(P0+hρg2)×(2R×h)]-2RT

  Force=2P0Rh+Rρgh2-2RT