# 9th Class Physics Chapter 7 Important Short Questions 2024

Students if you are looking for the 9th Class Physics Chapter 7 Short Questions Notes if yes? then you visit the right place where you can easily find Physics Chapter No. 7 most important short questions without answers but it is your responsibility to find answers from your 9th class Physics book.

Students You know that these Chapter 7 Properties of Matter Short Questions of Physics are helpful so don’t ignore them to read from your Physics book of the 9th class where you are comfortable learning.

## 9th Class Physics Chapter 7 Short Questions Notes

• The kinetic molecular model explains the three states of matter assuming that
• matter is made up of particles called molecules.
• the molecules remain in continuous motion.
• molecules attract each other.
• At very high temperatures, the collision between atoms and molecules tears off their electrons. Atoms become positive ions. This ionic state of matter is called plasma-the fourth state of matter.
• Density is the ratio of mass to volume of a substance. The density of water is 1000 kgm.
• Pressure is the normal force acting per unit area. Its SI unit is Nm or Pascal (Pa).
• Atmospheric pressure acts in all directions.
• The instruments that measure atmospheric pressure are called barometers.
• The atmospheric pressure decreases as we go up. Thus, by knowing the atmospheric pressure of a place, we can determine its altitude.
• The changes in atmospheric pressure at a certain place indicate the expected changes in the weather conditions of that place.
• Liquids also exert pressure given by: P = p g h
• Liquids transmit pressure equally in all directions. This is called Pascal’s law.
• When a body is immersed wholly or partially in a liquid, it loses its weight equal to the weight of the liquid displaced. This is known as Archimedes principle.
• For an object to float, its weight must be equal to or less than the upthrust of the liquid acting on it.
• The property of matter by virtue of which matter resists any force that tries to change its length, shape, or volume is called elasticity.
• Stress is the deforming force acting per unit area.
• The ratio of the change of length to the original length is called tensile strain.
• The ratio between stress and tensile strain is called Young’s modulus.