PHYS_10_21_V1_LP_Center of mass

Statics

School:

Date:

Teacher name:

Grade: 10

Number present:

absent:

Theme of the lesson

Center of mass

Learning objectives that are achieved at this lesson

To find the canter of mass of the perfectly rigid body and system of material bodies

Lesson objectives

Students can:

- describe the moment of a force and give examples from everyday life;

- orally and in writing analyze the results of the study;

- Determine the center of gravity of an irregular shaped plane figure

Success criteria

Language objective

Lexicology and terminology:

Simple mechanisms, lever, block, inclined plane, screw, wedge, force, moment of force, arm of force, mass center, clockwise, counterclockwise, equilibrium (balance)Useful set(s) of phrases for dialogue/writing.

If you do ..., then I will do ...

Let's do … first, and then we can do ...

How about to do ...

What happens if we ...?

I agree / disagree with you.

Values instilled at the lesson

This Unit begins with a repetition of mass and weight. Then the students familiarize with the rotating forces, they explore the condition of equilibrium of bodies having an axis of rotation. Students will apply the equilibrium conditions in practical situations.

ICT skills

Using of ppt, integration of ICT

Previous learning

describe the moment of a force and give examples from everyday life;

Course of the lesson

Beginning

2 min

Organizational questions - LO, SC.

Teacher introduces the theme of the lesson and the lesson objectives/LO together with students using PPT 

Students to summarize main ideas, evaluate class processes, answer questions posed at the beginning of the lesson, and link both to the past and the future.

PPT slide 1-2

PPT slides 3-6

Middle

10 min

11 min

15 min

Topics Reviewed

Activity 1: Center of Gravity of a Student

Simple exercise to demonstrate the center of gravity of a person and how it helps us keeps balance.

Objectives: The students should be more aware of their own center of gravity and how it helps them balance. They should also begin to relate this to other objects.

Materials: A pen

Procedure:

1.      Ask a student to stand up against a flat wall. Place a pen on the floor in front of them. Make sure their feet are together and the backs of their feet touch the wall.

2.      Ask the student, “Where is your center of gravity?”  /the center of gravity of a person is over their feet/.

3.      Without bending their knees and without losing their balance, ask the student to try bending forward to pick up the pen.

Discussion/Explanation:

Almost immediately, the student will know they will not be able to pick up

the pen. Why? When they bend forward, they are shifting the center of gravity of their body forward. To keep their balance, their feet need to move forward.

At the beginning of the lesson, get the students to do simple experiments, described in the references of the resource or PowerPoint Presentation № 7-20. To explain what they saw, have them explore the concept of «Moment of Force»

I) Working with Internet resources. Offer students a step by step instruction of work with an interactive resource in pairs or individually, at the end, offer to discuss in pairs the viewed material.

Discussion:

What is center of gravity? The center of gravity G is a point which locates the resultant weight of a system of particles. 

What is composite body? A composite body consists of a series of connected simpler-shaped bodies, which may be rectangular, triangular, semicircular, etc.

How can we find the center of mass of any object or system?

What is useful about the center of mass?

Definition: Center of Gravity

The center of gravity of a collection of masses is the point where all the weight of the object can be considered to be concentrated. If (xcg,ycg) are the coordinates of the centre of gravity of a collection of point masses m1 , m2 , etc, located at coordinates ( x1,y1 ), ( x2,y2 ), respectively, then: 

(m1 + m2 + ..)gxcg=m1gx1 + m2gx2 +... 

(m1 + m2 + ..)gycg=m1gy1 + m2gy2 +...               

Equations imply that the torque about the origin would be the same if the entire weight acted through the center of gravity instead of acting through the individual masses.

Solving for the x -coordinate of the center of gravity:

Similary, the y-coordinate of the centre of gravity is:

PPT slides 7-13

http://class-fizika.narod.ru/van9.htm.

http://files.school-collection.edu.ru/dlrstore/669b5269-e921-11dc-95ff-0800200c9a66/5_11.swf

http://class-fizika.narod.ru/7_prmehispol.htm

http://files.school-collection.edu.ru/dlrstore/669b5267-e921-11dc-95ff-0800200c9a66/5_9.swf

PPT slides 14-20

End

2 min

Feedback: Box of questions and suggestion.

Reflection:

-       What has been learned

-       What remained unclear

What is necessary to work on

Differentiation – how do you plan to give more support? How do you plan to challenge the more able learners?

-       Assessment – how are you planning to check students’ learning?

Health and safety regulations

Fundamental level:

They know every object has a center of mass,  where the center of mass will be.

Intermediate level:

On the surface of the Earth, the terms center of gravity and center of mass are interchangeable. They define the exact same location of an object: the point at the center of the object's mass distribution

Advanced level:.

Stable equilibrium: A condition in which an object is in balance, and will return to balance if disturbed.

Static equilibrium: A condition in which an object is in balance and not moving.

Symmetry: Exact correspondence of shape on opposite sides of a dividing line or plane through a center or an axis.

Unstable equilibrium: A condition in which an object is in balance, and will not return to balance if disturbed.

Reflection

Were the lesson objectives/learning objectives realistic? Did all learners achieve the LO?

If not, why?

Did my plan of differentiation work well?

Did I stick to timings?

What changes did I make from my plan and why?

Use the space below to reflect on your lesson. Answer the most relevant questions from the box on the left about your lesson. 

During the lesson ensure classroom is well ventilated and has  good lighting,  lab safety rules given.

Reflection

Were the lesson objectives/learning objectives realistic? Did all learners achieve the LO?

If not, why?

Did my plan of differentiation work well?

Did I stick to timings?

What changes did I make from my plan and why?

Summary evaluation

What two things went really well (consider both teaching and learning)?

1: UsingactivitiesCenter of Gravity of a Student.

2: Asking students to comment or elaborate on one another's answers.

What two things would have improved the lesson (consider both teaching and learning)?

1: Grouping the students and assign them problems which they can collectively work on.

2: Asking questions based upon a Bloom's taxonomy approach, aligned to the relevant lesson learning objectives.

What have I learned from this lesson about the class orachievements/difficulties of individuals that will inform my next lesson?

Keeping questions at an appropriate level of difficulty; that is, at a level where most

students can experience a high degree of success in answering

I think about specific questions  can ask students in order to check for understanding and to write them down, and then paraphrase them so that I was are prepared to ask the questions in different ways.

A good differentiation on my lesson was the questions based on Bloom's taxonomy usage according to learning objectives.

When I prepare your lesson plan, next to each activity indicate how much time you expect it will take

Some textbooks confuse center of mass with center of gravity (CG), which is related to the effect of gravity on an object, while center of mass concerns mass distribution. Although CG is often at the same location as the CM, they are completely different concepts

I used the resources

https://www.teachengineering.org/lessons/view/cub_mechanics_lesson06