9th Physics New Book Chapter 6 Short Questions
9th Physics New Book Chapter 6 Short Questions Answer solution. Physics Class 9th New Book 2025 Chapter 6 Notes.
6.1 Why heavy animal like an elephant have a large area of the foot?
Animals like elephant have large area of foot to reduce the pressure they exert on the ground. Pressure is equal to force per unit area.
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6.2 Why animals like deer who run fast have a small area of the foot?
Animals like deer who run fast have a small area of the foot which results in high pressure on the ground. This high pressure provides better grip and speed.
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6.3 Why is it painful to walk bare footed on pebbles?
It is painful to walk bare footed on pebbles due to pebbles small surface area. Force ( weight of the body ) creates high pressure on small pebbles which causes pain at the point where pebbles contact with the feet.
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6.4 State pascal ‘s law? Give an application of pascal’s law?
Pascal’s law states that when pressure is applied at one point in an enclosed fluid, it is transmitted equally to all parts of fluid without loss.
Applications of Pascal’s law
i):- Air pressure spreads equally inside the balloon to make it expand.
ii):- Brust if tyre and hydraulic lift are also examples of Pascal’s law.
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6.5 State what do you mean by elasticity of a solid?
A object is said to be elastic, if after removal of the deforming force, it restores to its original size and shape. This property is material is known as elasticity.
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6.6 What is Hooke’s law? Does an object remains elastic beyond elastic limit? Give reason.
Hook’s law states that under the elastic limit the extension or compression of an elastic object is directly proportional to the applied force.
F=kx
where F is applied force.
k is spring constant.
x is the extension or compression.
An object does not remain elastic beyond the elastic limit becalastic limit is the maximum force that an object can bear while still returning to its original shape after the force is removed.
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6.7 Distinguish between force and pressure?
Force is an agency which changes or tries to change the state of an object. Pressure is the force per unit area.
Force is total push or pull while pressure tells us how concentrated the force is over the given area.
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6.8 What is the relationship between liquid pressure and the depth of the liquid?
$$P\;=\;\rho\;g\;h\;\\where\;P\;is\;pressure\;at\;depth\\\rho\;is\;density\;of\;the\;liquid\\g\;is\;gravitional\;acceleration\\and\;h\;is\;depth\;of\;the\;liquid$$
Liquid pressure increases with the depth. As depth h increases, more liquid is above at that point, so more weight is pressing down. This causes greater pressure on objects at lower depths.
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6.9 What is the basic principal to measure the atmospheric pressure by a simple mercury barometer?
Basic principal to measure the atmospheric pressure by a simple mercury barometer is that atmospheric pressure is equal to the pressure exerted by Mercury column in the barometer.
$$P\;=\;\rho\;g\;h\;\\where\;P\;is\;pressure\;at\;depth\\\rho\;is\;density\;of\;the\;liquid\\g\;is\;gravitional\;acceleration\\and\;h\;is\;depth\;of\;the\;liquid$$
The higher the atmospheric pressure the higher the Mercury rises in the tube.
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6.10 State the basic principal used in the hydraulic brake system of the automobiles?
Basic principal used in the hydraulic brake system of the automobiles is Pascal’s law. When pressure is applied to a liquid in a closed system, it is transmitted equally in all directions.
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