AP Board Class 9 Physical Science Chapter 8 Floating Bodies

In our daily lives, we must have noticed that some objects float on water while some sink? Why does this happen? Well, Chapter 8 of Class 9 Physical Science AP board textbook discusses this topic in detail and provides the right insight to the students. The chapter also covers topics like;

  • Buoyancy
  • Density and Relative Density
  • Air Pressure
  • Archimedes Principle
  • Pascal’s Principle


Buoyancy is defined as the force applied to the object in an upward direction. Usually, most of the objects experience a force of buoyancy, when they are immersed in a fluid and the object also appears to have lost its weight.


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

Relative Density

Relative density is said to be the ratio of the density of an object to the density of a standard substance let’s say water or air. By calculating the relative density, we can find out how many times each solid object is dense compared to water.

Air Pressure

Air pressure is the weight of air molecules that presses down on the surface of the earth. Generally, it is defined as the force exerted by the weight of the air.

Pascal’s Principle

According to Pascal’s principle, when an external pressure is applied to an enclosed body of fluid the pressure is equally transferred in all directions in every part of the fluid volume and the surrounding walls of the vessel.

Students can go through important chapter questions given below and learn about some interesting topics.

Question 1: What is the value of the density of water?

Answer: The value of the density of water is 997 kg/m3.

Question 2: What is the Archimedes principle?

Answer: Archimedes’ principle states that when a body is immersed in a fluid it experiences an upward force of buoyancy equal to the weight of the fluid displaced by the immersed portion of the body.

Question 3: Explain which is denser milk or water?

Answer: Milk is denser than the water. It is because milk’s density is more than the density of water.

Students can stay tuned to BYJU’s to learn all the important Class 9 Science topics and access various Andhra board study materials, including syllabus, exam timetable and more.

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