LESSON PLAN - SingaporeTeachersLearningCentre



Physics Lesson Plan

Topic: Introduction to Moment

In partial fulfillment of the requirements for

QCP 521 Teaching of Physics II

Lesson Plan

Topic : Turning Effect of Forces (Introduction to Moment)

Duration: 70 minutes (double period)

Target Class : Secondary 3 Express.

Instructional Objectives: At the end of lesson, students should be able to:

1. Describe the moment of a force in terms of its pivot, force applied and the perpendicular distance from the pivot to the line of action.

2. Describe some relevant daily life examples.

3. Define and calculate moments using formula [pic]

4. State and apply principle of moments for a body in equilibrium to solve problems.

Prior Knowledge : Before the lesson, students shall be able to:

1. State and apply Newton’s law of motion.

2. Interpret and construct force diagram.

3. Construct perpendicular lines from a point to a line.

New Concepts/Terms:

Learning Aids & Resources :

Set Induction : A half-metre rule

IT : i) PowerPoint slides and overhead projector

ii) Video demonstration on seesaw candle

Non-IT i) Worksheets (Appendices A, B, C)

ii) Whiteboard and markers

iii) Wrenches

Hands-on : 21 sets of the following apparatus:

a half-meter rule, a mass of 50g, a mass of 100g, string and scissors.

Set Induction :

• Ask students to observe and spot the difference in the way you drop the half-meter rule, as the following diagram depicts. One is to hold the meter rule at two ends and let go both ends simultaneously to allow free fall. The other is to hold the meter rule at two ends and release only one end, so the rule swings down towards the other end.

• Use this activity to introduce pivot and turning effect of forces (moment or torque)

• Get a student (probably a big guy) to open the classroom door as he usually does. Then ask him to open the door by only pushing near the hinge. He will realize it is extremely difficult to do so. If the class is not convinced, ask a few more students to try.

• Ask the class to identify the pivot in this case and note the turning effect of the push on the door. Get the class to see the difference is the distance from the pivot.

• Introduce the concept of moment or torque.

Lesson Development :

1) Everyday applications

The trigger activity uses the simple action of door opening to let students appreciate physics in our life. And more daily examples (wrench, crane, can opening etc) are introduced later to bring relevance of moment to the classroom.

2) Student participation

This will be a student-centred lesson whereby the class works in pairs to investigate the principle of moment. They will be given the necessary apparatus and worksheet (Appendix B) to deduce the relationship between clockwise moment and anti clockwise moment. Some students will also present their solutions to some problems on the board. This helps to keep the students on task and build up their confidence.

3) Experimental activities

The exploration activity on principle of moment provides hands-on experience and promotes inquiry thinking to enhance students’ learning.

4) Collaborative learning

After each pair has done the investigative activity, they will share their findings with the class and answer any questions pertaining to their findings.

5) IT – Interactive multimedia

The lesson will use PowerPoint slides as visual aides and show a video demonstration of seesaw candle to illustrate the principle of moment.

Lesson Closure:

Get the class to reflect on their learning and share with the class. Summarize the main objectives of the lesson.

References:

• GCE ‘O’ Levels Physics Syllabus (5052)

• Video demonstration of seesaw candle

Lesson Plan Proper

Microteaching session is highlighted in italics.

|Time Frame |Teaching/Learning Activities |Materials |Rationale |Key questions |

|(min) | | | | |

| | | | | |

| |Induction Activity: | | | |

| | | | | |

| |Ask students to observe and spot the difference in the way you drop the half-meter rule. | | | |

|5 |One is to hold the meter rule at two ends and let go both simultaneously to allow free | | |What’s the main difference in the way I|

| |fall. The other is to hold the meter rule at two ends and release only one end, so the |Half -Meter Rule |By comparing two different types of falling, it |drop the rule? |

| |rule swings down towards the other end. | |introduces pivot and turning effects of forces to |How would you describe the motion of |

| | | |the students. |the rule? |

| | | | | |

| |Get a student (probably a big guy) to open the classroom door as he usually does. Then | | | |

| |ask him to open the door by only pushing near the hinge. He will realize it is extremely | | | |

| |difficult to do so. Ask class to think of some daily life examples of moments. | | |What has changed in these two different|

| | |Blackboard and marker |This simple everyday example brings relevance of |ways of opening the door? |

| |Show two wrenches, one with long arm, the other with short arm. Ask students which wrench| |moments to our life and get students examine the |Could you identify the pivot in this |

| |would they choose to unscrew a bolt. | |rationale behind. |case? |

| | | | | |

| | |Wrenches | | |

| | | | | |

| |Development of Concepts: | | | |

| |Definition and Calculation of Moments | | | |

| |Introduce the definition of moments (formula and units), stressing on the meaning of | | | |

| |“perpendicular distance”, and comparing with the definition of work done. Go back to the | | | |

|5 |examples of two wrenches with different length and door-opening activity, ask students to | |Through comparing to formula of work done, it |Have you seen the formula somewhere |

| |apply the formula to explain that the moment required to turn an object is fixed, while | |promotes lateral thinking and linkage to prior |else? Also involves force and distance?|

| |distance is longer, force required will be less. | |knowledge. |Why do you feel it’s harder to open the|

| | |Whiteboard and markers | |door if you push near the hinge? |

| | | | | |

| |Show some daily life examples of moments, get students to identify the pivot, the force | | |Is this the correct way of drawing |

| |and construct the perpendicular distance. During the construction, the line of force can | | |perpendicular distance? (non-example) |

| |be extended if necessary. Can ask students to present their answer on the transparency. |Worksheet appendix A (OHT)| | |

| | | |Make sure students understand the perpendicular |Which direction shall I apply the |

|10 |Using wrench example, ask students to choose the direction to apply force on the wrench. | |distance is from pivot to the line of force by |force? F1, F2 or F3? |

| |At the same time introduce clockwise and anticlockwise moments using the wrench example. | |showing the examples. | |

| | | | | |

| | |Wrench, Clock (in | |What happened if I change the question |

| |Let students try some simple questions on calculation of moments. Ask a few students to |classroom) |Let students realize that force and distance will |to “find the moment about point B |

|5 |present their answers on the board if time allows. And use the working examples to | |influence the outcome of turning effects. |instead”? |

| |investigate moment about different points, students will realize the importance of | |Use clock to illustrate the direction of moments. | |

| |identifying the pivot. | | | |

| | |Whiteboard and markers | | |

| | |Worksheet appendix C |It’s easier for students to visualize and |Have you ever noticed how a crane keeps|

| |Principle of Moments | |understand using numerical examples. |its balance? |

|10 | | | | |

| |Recall the concept of clockwise and anticlockwise moments, show pictures of cranes to let | | | |

| |students ponder how to balance the moments. | | | |

| | | | |Is there any pattern you have |

| | | | |recognized? |

| |Inquiry Activity (Pairwork) |PowerPoint slides | | |

| |Give clear instructions and expectations before grouping the students. Ask one student to | |Visual aides to show real life application of | |

| |tie the string at 25 cm mark to keep the rule balanced. Then put the 100g at one side of | |moments. | |

| |the string and the 50 g on the other side to keep the rule balanced. The other student | | | |

| |fills the data table in the worksheet to record down the mass and the corresponding |PowerPoint Slides | | |

|5 |distance. Let the students share their findings and induce the principle of moments. |Half-meter rule, string, | | |

| | |50g and 100g masses. | | |

| |Ask the students to draw the force diagram of their experiment. Highlight the presence of| |The inquiry and induction approach is taken here | |

| |gravitational force on all objects on earth. If the gravitational force is passing |Worksheet appendix B |to let students investigate the principle of | |

| |through the pivot, no moment is resulted due to zero distance. Relate the previous crane | |moments themselves. This is to promote a sense of |Are these all the forces present on the|

|15 |example and ask students to apply the principle to explain how the crane keeps its | |ownership towards students’ learning. |rule? |

| |balance. Show the video of seesaw candle to get students explain the observation. |Worksheet appendix B | |Why is the candle seesawing? |

| | | | | |

| |Show one working example using principle of moments. Ask students do a few more |Video clip (Seesaw Candle)| | |

| |questions, in increasing difficulty. | | | |

| | | |Pointing out students’ common mistakes helps them | |

| | | |to avoid making the same mistakes. | |

| | |Worksheet appendix C | | |

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|10 | | | | |

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| | | |Practice to reinforce the concept. | |

| | | | | |

|5 |Closure: | | | |

| |Let students write down their reflection of the lesson. Then ask a few students to share | | | |

| |what they have learnt from this lesson. | |Encourages reflective learning and makes learning |What are the most important things you |

| | | |more conscious and visible to the students. |have learnt in this lesson? |

| | | | | |

| |Summarize the concepts taught in this lesson: the definition of moments, its application | | | |

| |in our daily life, the principle of moments. | | | |

| |Ask students to finish the questions in the worksheet as homework. Tell them that you | | | |

| |will check their work in the next lesson. | | | |

Microteaching Reflection

Through the process of micoteaching, I have learnt the following points:

• Be very thorough and confident about the content I am teaching. I realized that students could ask any questions related or non-related to the topic you are teaching, thus it’s essential to be very familiar with the content and prepare beyond the requirement of the syllabus. For example, only by observing my colleague’s microteaching, I realize some of my misconceptions, like speed of wave is only affected by the medium it is traveling, not by the wave’s frequency or wavelength as the equation may have suggested [pic].

• Listening to my colleague’s microteaching, I realize the importance of student-centred teaching. There are various ways to engage the students, like doing investigative activities, getting feedback from the students, showing video clips or simulations. In comparison, real life demonstration is more effective to bring the message across than a demonstration video clip.

• Lesson plan helps greatly in structuring the lesson and smooth transition of the contents. It makes me conscious to decide the flow of the ideas so that students can follow the concepts and don’t get lost in the lesson. The lesson plan also helps me to identify the rationales behind each teaching activities, so that it’s clear to me which skills are not developed in the lesson and helps me to improve my teaching approaches.

• In demonstration or illustration of concepts, it’s important to convince the students what you are saying is true, like if you have two magnets, you tell students one magnet is stronger than the other, to verify this, you show that the stronger magnet can attract a lot more paper clips than the weaker magnet. This helps students to clear their doubts and believe in what they are seeing.

• I also note that if the demonstration produces quite a few results or you have quite a few questions related to the demonstration, it’s beneficial to record the observations or students’ answers on the whiteboard. This helps students to stay focused and also makes it much easier for you to refer to while illustrating the concepts.

I find the microteaching very helpful and beneficial, it opens my mind to various ideas of teaching physics topics and brings my attention to some common pitfalls. Through sharing and observation, we learnt each other’s strength and weakness.

Appendix A Daily Application of Moments

Draw on the following diagram the pivot, the force and the perpendicular distance.

Indicate whether the direction of the moment too, clockwise or anticlockwise.

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Appendix B Investigation on Principle of Moments

Objectives:

• To analyze the effects of clockwise and anti clockwise moment

• To investigate the conditions to keep an object at equilibrium

• To induce the principle of moments

Apparatus:

• A half-metre rule

• A mass of 50g and a mass of 100g

• Some strings

1. Use the string to suspend the rule, make sure the rule is balanced. At which marking shall you tie the string?

| |

2. Place the 50g mass anywhere on one side of the rule, what effect does it have on the rule? What’s the moment and the direction of the moment? Show your working clearly.

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3. Place the 100g mass on the other side of rule to keep the rule balanced. At which marking shall you put the 100g for this to work? What’s the moment produced by this 100g mass and the direction of the moment? Show your working clearly.

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4. Repeat step 2-3 five times and record the data in the following table. g = 10m/s2

Weight of 100g mass __________________ Weight of 50g mass____________________

| |1 |2 |3 |4 |5 |6 |

|Data set |Distance of 100g |Direction of moment |Moment produced by |Distance of 50g mass |Direction of moment |Moment produced by 50g|

| |mass from pivot (cm)|produced by 100g |100g mass about the |from pivot |produced by 50g mass |mass about the pivot |

| | |mass about the pivot|pivot (Nm) | |about the pivot |(Nm) |

|1 | | | | | | |

|2 | | | | | | |

|3 | | | | | | |

|4 | | | | | | |

|5 | | | | | | |

5. Did you observe any pattern in the values you obtained from column 3 and 6? How about column 2 and 5?

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6. Based on your investigation, what do you think are the necessary conditions for an object to be balanced (in equilibrium)?

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7. Draw a force diagram of the experiment while the rule is balanced with 100g and 50g masses on it. Indicate ALL forces acting on the rule.

Appendix C Exercises on Turning Effect of Force

1. Find the moment of the exerted force about the pivot O for the following situations, show your working clearly.

2. Find the moment of the exerted force about the pivot O for the following situations:

Hint: use trigonometry

3. A metre rule with uniform weight is balanced at its centre by two weights, X and Y as shown in the figure below. If the weight of X is 40 N and the weight of Y is 60 N, find the distance of weight Y from the support.

4. A metre rule with uniform weight is balanced by a weight, Z as shown in the figure below. If the weight of Z is 40 N and the weight of the ruler

5. A man of mass 72 kg stands on one end of a see-saw. Two children sit on the opposite end as shown in Figure 6. If the pivot is assumed to be smooth, which of the following gives the correct combination of the masses of the children that are able to balance the man?

Child A Child B

A 40 kg 50 kg

B 45 kg 42 kg

C 50 kg 40 kg

D 54 kg 54 kg

6. A painter of weight 1000N stands 1.0m from the left-hand end of a uniform plank which is 5.0m long and weighs 800N. The plank is supported by two trestles each 0.5m from the opposite ends. The diagram below shows the two upward forces P and Q acting on the plank due to the trestles.

7.

8.

9.

(a) Complete the diagram above to show any other forces which are acting on the

plank. Name each of these forces.

(b) What is the magnitude of the total downward force exerted on the trestles?

(c) What is the magnitude of the total upward force exerted by the trestles on the

plank?

(d) By taking moments about the left trestle, calculate the upward force exerted on

the plank by the other trestle.

-----------------------

O

0.25 m

half-metre rule

hand

calculated by

[pic] [SI units: Nm]

can be

Anti-clockwise

is also known as

spoon

hand

Tin can

lid

Clockwise

Moment or Torque

Turning Effect of Forces

d

0.3 m

30(

10 N

1.5 m

O

1.3 m

1.5 m

5 N

effort P

effort

O

5 N

1.5 m

O

5 N

1.5 m

O

5 N

1.5 m

0.75 m

60N

40N

0.1 m

W

40N

B

A

Man

0.50 m

1.00 m

1.50 m

0.5m

0.5m

Q

P

Done by:

Lecturer:

Supervisor:

Date:

Cao Huijie (S7879403H)

A/P Yap Kueh Chin

A/P Chen Lai Keat

October 21, 2005

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