Q. 5

# 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 :

(a) Here, we are removing the atmospheric pressure.

Hence, pressure at the bottom of the glass,

Therefore, the downward force is given by .

For the second case, the vertical force is equal to the weight of the water,

The horizontal forces again cancel out. So the total upward force is,

The total force on the bottom depends only on the height of the vessel, the bottom area and the weight of the water. As density of water is fixed, the total force thus depends on the volume of the container. These quantities can remain same for different shapes and hence the answers do not depend on the shape of the container.

Rate this question :

The weight of an empty balloon on a spring balance is W_{1}. The weight becomes W_{2} when the balloon is filled with air. Let the weight of the air itself be ω. Neglect the thickness of the balloon when it is filled with air. Also neglect the difference in the densities of air inside and outside the balloon.

A solid float in a liquid in a partially dipped position.

HC Verma - Concepts of Physics Part 1Streamline flow is more likely for liquids with

Physics - ExemplarPressure is a scalar quantity because

Physics - ExemplarIn the derivation of P_{1} - P_{2} = ρgz, it was assumed that the liquid is incompressible. Why will this equation not be strictly valid for a compressible liquid?

A metal piece of mass 160 g lies in equilibrium inside a glass of water (figure 13-E4). The piece touches the bottom of the glass at a small number of points. If the density of the metal is 8000 kg m4, find the normal force exerted by the bottom of the glass on the metal piece.

HC Verma - Concepts of Physics Part 1