Home 9th Class Physics Notes 9th Class Physics Chapter 7 Notes, Short Questions, and Numerical

# 9th Class Physics Chapter 7 Notes, Short Questions, and Numerical

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This is a simple post about Physics Notes of 9 Class. This post Contains 9th Class Physics Chapter 7 Notes – Short Questions and Numerical7 for the students. You can add these short questions to the list of your preparation for exams.

## 9th Class Physics Chapter 7 Notes, Short Questions, and Numerical

Chapter 6 Short Questions and Answers are available here.

### Q.1: Write some important features of the kinetic molecular model of matter.

Ans.
(I) The matter is made up of particles called molecules

(II) The molecules remain in continuous motion

(III) Molecules attract each other

### Q.2: Define Hook’s law.

Ans. The strain produced in a body by the stress applied to it is directly proportional to the stress within the elastic limit of the body.

### Q.3: The mass of volume 200cm³ of stone is 500g. Find density.

Ans.
m=500g        v=200cm³
Density            =Mass/Volume
=500g/200cm³  =  2.5g cm⁻³

Thus the density of stone is 2.5g cm⁻³

### Q.4 Define density.

Ans. The density of a substance is defined as its mass per unit volume.

### Q.5: Why water is not suitable to be used in a barometer?

Ans. Water has a smaller density. Therefore, the height of the water column in the tube of barometer would be very large about 10m which becomes inconvenient. Therefore, the use of water in the barometer is not suitable.

### Q.6: Why does the piece of stone sink in water but a ship with a huge weight floats?

Ans. When a piece of stone is placed in the water, then upwards thrust acting on it due to water is much smaller because the weight of water displaced as less than the weight of the piece of stone. Whereas the shape of the ship is made such that the weight of water displaced is much greater than the weight of the ship. So that upwards thrust because large, as compared with the weight of the ship and it floats over the water surface.

### Q.7: Define pressure and give its unit.

Ans. The force acting normally per unit area on the surface of a body is called pressure.

Unit: Unit of pressure is Nm⁻²

### Q.8: State of Pascal’s Law.

Ans. Pressure applied at any point of a liquid enclosed in a container is equally transmitted without loss to all other parts of the liquid.

### Q.9: Write down any two examples of the application of Pascal’s Law.

Ans.
(i) Hydraulic press

(ii) Hydraulic jack

### Q.10: Define gas plasma.

Ans. Atoms of gas lose their electrons and become positive ions. This ionic state of matter is called plasma.

### Q.11: What is density? What is its unit in System International?

Ans. The density of a substance is defined as its mass per unit volume.

Unit: Unit of density is kilogram per cubic metre (kgm⁻³)

### Q.12: State the kinetic molecular model of matter.

Ans. The kinetic molecular model is used to explain the three states of matter – solid, liquid and gas.

Solved MCQs of Physics Chapter 6 for Class 9 are also available.

Above available Short Questions are taken from Al-Hassan Super Notes Physics (English Medium) – IX

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