Question

Suppose the glass of the previous problem is covered by a jar and the air inside the jar is completely pumped out. (a) What will be the answers to the problem? (b) Show that the answers do not change if a glass of different shape is used provided the height, the bottom area and the volume are unchanged.

Answer 1

(a) The atmospheric Pressure will be zero in the container.

Therefore, the pressure of water at the bottom of the glass = ρgh

Pressure  = 1000 × 10 × 0.2  Pa.

= 2000 Pa.

 Now, Using the Formula, Pressure = Force/Area

∴ Force = Pressure × Area

Force = 2000 × 2/1000

Force = 4 N

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(b) The resultant vertical force by the glass on the water = weight of the water

= 0.50 × 10 N

= 5 N.  

Hence the force by the side of the glass on the water  

= 5 - 4

= 1 N

Hope it helps .