3.1 Under Tan Ding Pressure

Problems/misconception/challenge faced by the students 1. Problem: Students are not able to distinguish between force and pressure. 2. Misconception: Bigger force always associates with bigger pressure. Construction of concept through effective questioning Topic: Approach: Method: Strategy: Suggested Activity:

Understanding Pressure. Constructivism Effective Questioning Technique. Perform a simple activity followed by effective questioning technique to build the concept of pressure. Students are asked to press both ends of a pencil with equal force.

1. What is pressure? (Accept any answer) Suggested activity: Students are asked to press both ends of a pencil with equal force. 2. Which end causes more pain to your finger? (Sharp end) 3. Why? (Sharp end has smaller surface area) 4. What is the relationship between the surface area and the pain experienced by your finger? (Smaller surface area, more pain) Note: Student associates pain with pressure. More pain means more pressure exerted on the finger. 5. Which end exerts bigger pressure? (Sharp end) 6. What is relationship the relationship between the pressure and surface area? (The smaller the surface area, the bigger the pressure)

7. What will feel if you press both ends with a bigger force? 8. What is the relationship between the force and the pressure? (The bigger the force, the bigger the pressure)

Date: SUBJECT: PHYSICS YEAR:

FORM 4

LEARNING AREA:

3. FORCES AND PRESSURE

LEARNING OBJECTIVE:

3.1 UNDERSTANDING PRESSURE

LEARNING OUTCOMES:

Students should be able to: 1. conceptualise and define pressure as P =

F . A

2. solve quantitative problems involving pressure. 3. describe applications of pressure. Time:

2 periods (80 minutes)

Subject Content:

Pressure

Suggested Activities:

1. Students are asked to press both ends of a pen with equal force. 2. Questions will be posed orally in logical sequence so that students can construct the concept of pressure. 3. Discuss the definition of pressure as P =

F based on the concept built in Activity 2 A

4. Teacher discuss some examples of quantitative problems solving involving pressure. 5. Students discuss in group to get some applications of pressure in daily life.

Moral Values:

Being cooperative

Creative and Critical Thinking Skills: Relating, making generalisation, conceptualisation & problem solving. Teaching Aid: STAGES / STEPS Set Induction (10 minutes)

Computer and LCD projector. CONTENT

SUGGESTED ACTIVITIES 1. State the learning outcome from the teaching courseware. 2.

A pair of high heel shoes

walk on a sand pit using her school shoe. The same

and a tray of sand or sand

student then walk on the sand pit again by putting on a

pit

Students make observation.

4. Teacher poses these questions : (a) Which type of shoes produces a deeper foot print on the sand pit? (b) Why do you think so? ( Accept any answer )

Development

REMARKS Computer and LCD

Using simple demonstration by asking a girl student to

pair of high heel shoes. 3.

RESOURSES /

1. Students are asked to press both ends of a pen with equal

(70 minutes)

force.

Pen

2. Teacher poses the following questions orally to the class STEP 1

Conceptualize

to built understanding of pressure through constructivism.

(20 minutes)

and define

(a) What is pressure? ( Accept any answer )

pressure as

(b) Which end causes more pain to your finger?

P=

(sharp end)

F A

(c) Why do you think so? (d) Which end has smaller surface area? (e) What happen to the pain you experienced when the surface area in contact is smaller? (f) Which end do you think exert bigger pressure on your finger?

To build concept of

(g) What happen to the pressure exerted on your finger

pressure increases when

when the surface area in contact is smaller?

the surface area in contact

(h) Can you state the relationship between the surface

decreases.

area and the pressure? 3.

Students are asked to press both ends of the pen with bigger force. Then pose the following questions orally to the class or to individual students. (a) What do you feel when press with bigger force?

(b) What can you say of the pressure exerted on your finger when force increases? (c) What relationship do you think exist between

Students construct idea

pressure and force?

that pressure increases with force.

4. Teacher leads students to conceptualize pressure which is directly proportional to the force (F) and inversely proportional to the surface area (A) based on the experience and discussion through questioning sequence above. 5. Conclude this part of the lesson by stating that pressure is defined as force per unit area, i.e P = Nm-2 or Pascal (Pa).

F and its SI unit is A

Deducing the mathematical relationship between Pressure ( P ), Force ( F ), and Surface Area in contact ( A ).

STEP 2

Problem solving

(30 minutes)

1. Teacher discusses a few examples of quantitative problems involving pressure. (Refer to Appendix 1 ) ( 10 minutes ) 2. Students try Mastery Practice 3.1 Q1 & Q2.(Text Book) in the class to reinforce understanding of the concept.

( 15

minutes ) 3. Students are encouraged to look for extra exercises involving pressure from the reference book or past year paper. STEP 3

Applications of

(15 minutes)

pressure

1. Teacher discusses with students the applications of pressure in daily. Examples : •

The blade of a knife has a very small area that exerts such high pressure that the meat can be cut easily.

• The sharp tip of a thumbtack has a very small area in contact with the board. Hence the tip can pierce through the board due to the high pressure it exerts. • You will not sink into the snow if you are wearing

skis. The pressure exerted is low due to the large surface area of the skis. • The large tracks of a bulldozer help to reduce pressure so that the heavy bulldozer will not sink into the soft ground. 2. Students are encouraged to participate in the class discussion and give their own experiences in daily lives that Closure

involve application of pressure. 1. Evaluation of understanding of pressure using teaching

(10 minutes)

courseware.

Computer & LCD

2. Show the conclusion of what the students have learnt from this topic from the teaching courseware. .

Appendix 1 Q1. Diagram below shows the dimensions and the weight of a wooden block resting on the floor. Calculate

(i) the maximum pressure exerted. (ii) the minimum pressure exerted. Weight = 24 N

4m

2m 3m Q2. A student is pressing a thumbtack into a notice board with a force of 15 N. The area of the head and the tip of the thumbtack is 0.0001 m2 and 1×10-6 m2 respectively. (i) Calculate the pressure exerted on the student’s thumb. (ii) Calculate the pressure exerted by the thumbtack onto the notice board. (iii) What causes the difference in pressures calculated in part (i) and (ii).

Summative Test

1. Pressure is defined mathematically as P =

F , where F is the force and A is the surface area in contact. What is the SI unit for A

pressure? 2. Explain how the webbed feet of a duck helps it to move around more easily on the muddy ground. 3. A four legged table of 200 N has a total cross sectional area of 40 cm2. What is the average pressure exerted by each leg of the table to the floor? 4. What is the minimum pressure exerted by the block onto the floor in the diagram below.

1.2 m

0.4 m 0.6 m 5. List down four examples of the applications of pressure in our daily life?