State of Matter and Pressure

ðŸ‘‰Â All Chapter ContentsÂ ðŸ‘ˆÂ

• 5.1 Pressure
• 5.2 Density
• 5.3 Pressure in liquids
• 5.4 Air Pressure
• 5.5 Elasticity
• 5.6 Three States of Matter: Solid, Liquid, and Gas

What is buoyancy?

If a body is immersed partly or completely in liquid or gas a thrust acts vertically upward in it. This upward thrust is known as buoyancy.

Write down the law of Pascal?

External pressure applied to any portion of a liquid or gas enclosed in a container is equally transmitted in all direction in the liquid or the gas without any trace of diminution and acts perpendicularly on the surface of the container in contact with the liquid or gas.

Write down Archimedes principle.

If a body is partly or fully immersed in a liquid or gas in equilibrium, it seems to have lost a part of its weight. This apparent loss of weight is equal to the weight of the displaced liquid or gas.

What is stress?

Whenever an external force deforms a body, an internal resistive force will develop inside the body due to its elastic property. This opposing force comes into play to resist the applied external force. This developed internal resistive force acting perpendicularly per unit area of the body is called stress.

Which quantity is pressure?

Pressure is a scalar quantity.

What is elastic limit?

There is a certain limit of the deforming force and if the force applied exceeds the limit the body then becomes unable to regain its previous shape and size. This limit of applied force is called elastic limit.

What is the unit of strain?

Strain has no unit cause strain is the ratio of two similar quantity.

Why does a body seem lighter when it is sunk in water?

We know, a body is easy to move in water but it is not that much easy to move when it is out of water. The body is felt considerably lighter in immersed condition as upward thrust acts on it. Therefore, the thrust acting vertically upward is equal to the weight of equal volume of water displaced by the submersed body. For this reason an immersed body apparently loses its weight, so it seems lighter in water.

Explain the floatation and immersion of a body in water.

Two forces act simultaneously on a body when it is released in a liquid at rest. The weight of the body, w1 acts vertically downwards. The buoyancy w2 acts vertically upward on an immersed body. There are three conditions of floatation and immersion of a body -

a) If w1 > w2, i.e. when the weight of the body is grater than the buoyancy of liquid, the body sinks. In this case the weight of the body is more than the weight of the displaced liquid.

b) If w1 = w2, i.e. when the weight of the body equals to the buoyancy of the liquid, the body floats being fully immersed in liquid. In such situation the weight of the body is equal to the weight of the liquid displaced.

c) If w1<w2, i.e. the weight of body is less than the buoyancy of liquid, the body does not sink. It floats being partly immersed in liquid. In such a position the weight of the body is less than the displaced water.

Write the uses of hydraulic press.

The uses of hydraulic press are given below-

i) To compress cloth bundle, cotton bundle, jute bundle, etc. by applying force hydraulic press is used.

ii)To obtain oil from seeds, it is used.

iii) To tighten leather and in many other things hydraulic press is used.

iv) To move the heavy part of engine up and down, it is used.

Why is it easier to lift up a body in water than in air?

It is easy to lift up a body in water than in air. We know, when we immerse a body in water a upward thrust act on it. The weight of the body and the buoyancy act in the same straight line but in opposite direction. For this reason the weight of body decreases. So, it is easier to lift up a heavy body in water than in air.

Why does rotten egg float on water?

The floatation and immersion of a body depends on the density of the body and liquid. If the density of body is greater than that of water then it will sink in the water, if it is not then it will float. The density of rotten egg is less than that of water, so it floats on water.

5.1 Pressure

• What is pressure?
• What is the unit of pressure?
• What is the dimension of pressure?
• What do you understand by 1 pascal?
• What is the area?
Mathematical Problems:

5.2 Density

• What is density?
• What is volume?
• Uses of density in our daily life.
• What do you understand by the density of water is 1000 kgm-3?
• What do you understand by the density of gold is 19300 kgm-3?
• How can we determine whether the eggs are good or rotten by submerging in water - explain.
Mathematical Problems:

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