Question

A closed vessel is half filled with water. There is a hole near the top of the vessel and air is pumped out from this hole.

• A. The water level will rise up in the vessel.
• B. The pressure at the surface of water will decrease.
• C. The force by the water on the bottom of the vessel will decrease.
• D. The density of the liquid will decrease.

Answer 1

Answer: (B), (C)

The pressure at the surface of water will decrease.
The force by the water on the bottom of the vessel will decrease.

The pressure on water surface will decrease because there will be less air molecules exerting pressure on the surface.
Also, the force on bottom will decrease because there is no more force of air molecules in the net total force exerted on the bottom.