**Archimedes’ Principle**

**General Aims**

- To develop interest of students in physical science.
- To develop an inquiry spirit in the students.
- To help students to see the physical science in relation to the rest of the culture.
- To develop interest in questioning.
- To develop critical thinking and scientific attitude.
- To develop supervisory ability in students.
- To develop problem solving skills in students.
- To make the students aware about inventions in the field of physical science and acquaint them with the knowledge of different streams of physical science.

**Specific Objectives**

- Students will be able to state Archimedes’ principle.
- Students will be able to enlist the application of Archimedes’ Principle.
- Students will be able to solve the problems of relative density.

**Teaching Aids**

Chart paper, Roller board, pointer and other useful classroom equipment.

**Previous Knowledge**

Students are already aware about Buoyancy.

**Introductory Questions**

Pupil-Teacher Activity |
Student’s Response |

Q1. What happens when an object is dipped in water? |
It feels lighter than its weight. |

Q2. Which force acts on the dipped objects in water? |
Buoyant force. |

Q3. Which principle is based on the working of buoyant force? |
Archimedes principle. |

**Statement Of Aim**

So, today we are going to study the topic ‘Archimedes’ Principle’.

**Presentation**

**Teaching point 1: Archimedes’ Principle**

Archimedes’ principle states that-

*“When an object is immersed fully or partially in a fluid, it experiences an upward force that is equal to the weight of the fluid displaced by it.”*

The principle is most frequently applied to study the behaviour of objects in water and helps to explain the floating and sinking, and why objects seem lighter in water.

When in fluids, the object experiences two forces:

- The actual weight which acts downwards.
- And, the buoyant force which acts upward.

**Teaching point 2: Application of Archimedes Principle**

Archimedes principle has many applications; some of them are as follows:

- It is used in designing ships and submarines.
- It is used in lactometer which is used to determine the purity of a sample of milk.
- It is used in hydrometer, used for determining the density of liquids.

**Teaching point 3: Relative Density**

We know that, density of substance is defined as mass of a unit volume.

The unit of density is** kg/m ^{3}**.

The density of a given substance under specified conditions remains the same.

The relative density of a substance is the ratio of its density to that of water.

Relative density has **no unit**.

**Blackboard Summary**

- Archimedes principle explains the sinking and floating of objects.
- Objects in fluid experiences buoyant force in upward direction.
- Archimedes’ principle is used in designing ships, submarine and also in lactometers and hydrometers.
- Mass and substance per unit volume is its density.
- Relative density has no unit.

**Classroom Supervision**

Pupil-teacher will supervise the students work and solve the problems of the students.

**Evaluation Questions**

**Q1. **Which upward force is exerted by fluid?

**Q2.** Instrument used for measuring density of water is called ___________.

**Q3. **Submarines and ships are based on ________________ principle.

**Q4.** Object in fluid exerts buoyant force acting downwards. **(True/False)**

**Q5.** Unit of relative density is:

- Kg
- Kg/m
^{3} - No unit
- Newton

**Home-Work**

**Q1.** State Archimedes’ Principle and write three applications of Archimedes’ principle.

**Lesson Plan- Important Link**

- States of Matter lesson plan- Class IX NCERT with pdf
- Mixture- INTEGRATED LESSON PLAN- CLASS 9th SCIENCE NCERT
- Complete Lesson Plan of Thomson’s atomic model Class IX
- Complete Lesson Plan of Solution NCERT Class IX
- Complete Lesson Plan of COLLOIDAL SOLUTION of Class IX
- Complete Integrated Lesson Plan of ELEMENTS of Class IX
- Complete Integrated Lesson Plan of ATOM of Class IX
- Integrated Lesson Plan of MOLECULES of Class IX
- Uniform Circular Motion- Complete Integrated Lesson Plan

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