9th Class Physics Chapter 6 Solved Question Answer
9th Class Physics Chapter 6 Solved Question Answer. We will solve all long questions. The answers are written in easy language to help the students of 9th class physics Punjab board students. They will understand the concepts very easily and prepare for their exams. You will learn about Hook’s law, Pascal’s law and their applications and examples, mercury barometer and manometer. You will also learn about pressure on a liquid and atmospheric pressure. Some important link are also given at the end of the post.
9th Class Physics Chapter 6 Solved Question Answer
6.1 What is Hooke’s law? Give three applications of this law.
Hook’s law states that within the elastic limit, the extension or compression of an elastic body is directly proportional to the applied force.
$$F\propto x\\F=kx$$
where k is constant of proportionality, called spring constant. k=F/x
Three applications of Hook’s law
1) Spring balance: It is used to measure the weight of an object.
2) Vehicle suspension system: Springs absorb shocks and vibrations.
3) Mechanical devices: Springs are used in clocks and watches.
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6.2 Describe the working and applications of a simple mercury barometer and a manometer.
Simple Mercury Barometer
Working
It consists of a glass tube fixed with mercury and closed at one end. The tube is inverted in a mercury-filled container. Some mercury falls, leaving a vacuum at the top of the tube.
Applications
It measures atmospheric pressure. It helps predict changes in weather. It is used to determine the altitude of a place.
For mercury barometer
$$P_{atm}=\;\rho gh$$
Manometer
Working
A manometer consists of a u-shaped tube partially filled with mercury or any other liquid. Its one end is connected to a gas container and the other is open to the atmosphere. The difference in the liquid level in two arms is used to measure gas pressure.
Applications
It measures the pressure of gases in containers. It measure the difference in pressure between two points. It is used in industries and laboratories to measure gas pressure.
For manometer
$$\triangle P=\;\rho gh$$
9th Class Physics Chapter 6 Solved Question Answer
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6.3 Describe Pascal’s law. State its applications with examples.
Pascal’s law states that when pressure is applied to an enclosed liquid, it is transmitted equally in all directions.
Applications of Pascal’s law
Hydraulic press
It is used to compress or press materials with a large force. For example compressing cotton into bales.
Hydraulic brakes
they are used in vehicles to apply brakes by transmitting pressure from brake pedal to the wheels.
Hydraulic lifts
It is used to lift heavy objects with a small force. For example lifting cars in workshop.
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6.4 On what forces the pressure of a liquid in a container depend? How is it determined?
The pressure of a liquid in a container depends on density, gravitational acceleration and depth. liquid pressure is directly proportional to all these factors.
$$P\propto\rho,\;\;P\propto g\;and\;P\propto h$$
After combining all these, we get
$$P\propto\rho gh\\P=\rho gh\\$$
Here constant of proportionality is 1.
$$\rho\;is\;density\;of\;liquid\\$$
g is gravitational acceleration and h is vertical depth of the liquid.
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9th Class Physics Chapter 6 Solved Question Answer
6.5 Explain that atmosphere exerts pressure. What are its applications? Give at least three examples.
Atmospheric pressure is the pressure exerted by the weight of air around us and on Earth’s surface.
Syringe
When the piston is pulled back, atmospheric pressure pushes medicine into the syringe.
Drinking straw
When we suck air through the straw, the pressure inside it decreases. Atmospheric pressure pushes the juice up through the straw into our mouth.
Dropper
Atmospheric pressure pushes liquid into the dropper when its rubber bulb is released.
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Check! Some important links below
