Learning Objective: 3.5 Applying Archimedes’s Principle

Method: Constructivism (Set Induction)

Approach: Demonstration/Role play

Activity: Demonstration

List of material/apparatus: Plasticine, polystyrene ball, beaker, water, pendulum bob

Demonstration 1 (Simple magic)

1. Use plasticine to make a solid ball.

2. Make another ball by wrapping a polystyrene ball with plasticine.

3. Drop the heavier ball into the beaker of water.

4. Take out this ball and purposely drop it on the floor.

5. While picking up the ball exchange it with the lighter ball without the students’ knowledge.

6. Then drop the lighter ball into the beaker of water.

7. The ball will float.

Demonstration 2

1. Use a polystyrene ball to show the concept of floating.

2. Pose this question to the students, “What happens if I put this polystyrene ball into water?”

3. A student is asked to put the polystyrene ball into water.

4. Pose these questions to the students, “What can you see?”, “Why is it floating?”

5. Then ask the student to press the polystyrene ball deeper into the water.

6. Pose this question to the students, “What do you feel?”

7. Then ask the student to release the ball.

8. Pose this question to the students, “What will happen?”

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Activity 1

1. Students are asked to imagine a floating ship and a piece of iron thrown into the sea. (Based on the photo above)

2. Based on the situation above, the following questions are posed to the students:

(i) Which one is heavier?

(ii) Which one has a larger volume?

(iii) Why is the ship floating?

(iv) Why does the iron sink? 3. Teacher and students discuss about the buoyant force, the weight of displaced

liquid and their relationship prior to introducing the Archimedes’ principle.

4. Students are to suggest any applications/natural phenomena based on the Archimedes principle.(Hydrometer/ Submarine)

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Summative Test Questions

1. The figure shows four spheres P, Q, R and S floating on water.

Arrange the density of the spheres in ascending order.

2. Figure (a) and Figure (b) show a spring balance supporting a metal block K in two situations.

Compare the buoyant force in Figure (a) and Figure (b).

…………………………………………………………………………………………………

3. It is easier to lift a heavy rock in water than on land. This is because the ……….

…………………….. in water is …………then on land.

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4. The diagram shows a boat floating in the river.

What will happen to the water level when it travels from the river to the sea? Explain your answer.

…………………………………………………………………

…………………………………………………………………

…………………………………………………………………

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