9th Physics Chapter 6 Comprehensive questions
9th Physics Chapter 6 Comprehensive questions. We will answer only revised syllabus 9th class physics.
6.1 What is Hook’s law? Give three applications of this law.
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6.2 Describe the working and applications of a simple mercury barometer and a manometer.
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6.3 Describe Pascal’s law. State its applications with example.
When pressure is applied at one point in an enclosed fluid, it is transmitted equally to all parts of fluid without loss. Its examples are hydraulic press, hydraulic brakes, hydraulic jack and hydraulic lifts.
Hydraulic press
it is used to lift heavy objects. When a small force is applied on a small piston, a large force is produced on a large piston. It is used to extract oils from seeds.
Hydraulic Brakes
Hydraulic brakes are used in vehicles. When brake peddle is pressed, pressure is equally distributed through brake fluid to all the wheels.
Hydraulic lift is used to lift heavy loads like cars. Hydraulic jack is also used to lift heavy vehicles to change the tyre.
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6.4 On what factors the pressure of a liquid in a container depend? How is it determined?
The pressure of a liquid inside the container depends on depth of the liquid, density of the liquid and acceleration due to gravity.
Lets check how to determine the pressure
Consider an area A of the liquid at depth h. The force acting on the area is equal to the weight of the liquid column over surface A.
Hence, volume of the liquid is V=Ah
If rho is the density of liquid, then mass of the liquid column will be
$$m=\rho V=\rho Ah\\Therefore,\;force\;acting\;on\\area\;A\;will\;be\\F=mg=\rho Ah(g)\\Pressure\;p\;at\;the\;area\;A\\will\;be\\p=\frac FA=\frac{\rho Ah(g)}A$$
$$p=\rho gh\\Where\\p\;is\;pressure\;of\;the\;liquid\\\rho\;is\;density\;of\;the\;liquid\\g\;is\;gravitional\;acceleration\\and\;h\;is\;depth\;of\;the\;liquid$$
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6.5 Explain that atmosphere exerts pressure. What are its applications? Give at least three examples.
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