"The Buoyancy of Water" PPT

"The Buoyancy of Water" PPT

Part One: Teaching Objectives:

1. Confirm that water and other liquids will have a buoyant effect on objects immersed in them, and confirm that air also has buoyancy.

2. Be able to explore the factors related to the size of buoyancy through experimental methods, and summarize Archimedes' principle.

3. Ability to measure buoyancy using a dynamometer and calculate buoyancy using Archimedes' principle.

4. Be able to deduce the conditions for objects to float and sink in liquids based on the relationship between force and motion, and use the conditions for objects to float and sink to explain relevant phenomena and solve simple practical problems.

Teaching focus

There are many formulas derived from physics knowledge, and once there are too many students, they will feel confused. Therefore, in the teaching process, the meaning of the letters represented by the formulas must always be emphasized, first in Chinese and then in letters.

When arriving at Archimedes' theorem, follow the steps of scientific inquiry.

For the state of objects in water, standardized expressions such as floating, suspending, sinking, etc. should be emphasized.

There are many experiments, and it is very important to guide students to think about experiments, such as the purpose of the experiment, why they should be done, etc.

The principle of density meter should be allowed to be explored by students themselves, which will also consolidate the previous knowledge.

Buoyancy of water PPT, part 2: buoyancy

Why don't people who can't swim drown in the Dead Sea?

Why do submarines float freely in the water?

experiment:

How does your hand feel when you press a tightly screwed empty mineral water bottle into the water?

What will happen to the bottle after it is released?

Question 1: What does the above phenomenon indicate?

Objects that float in water experience an upward buoyant force.

Question 2: Are objects such as stones and iron blocks sinking in the water also affected by buoyancy?

in conclusion:

Objects that sink in water also experience an upward buoyant force.

All liquids exert an upward buoyant force on objects immersed in them.

Buoyancy of water PPT, part 3: What is buoyancy?

The upward force exerted by the liquid on an object immersed in a liquid is called buoyancy.

Inquiry and learning:

Ask the question: What factors are related to the size of buoyancy?

Experimental program:

How to measure buoyancy?

F float = G - F pull

Explore: The relationship between buoyancy and water displaced by objects

Buoyancy of water PPT, part 4 content: Archimedes' principle

An object immersed in a liquid experiences an upward buoyant force equal to the gravity of the liquid displaced by the object.

Formula: F float = G drain = ρ liquid g V drain

It can be seen from the formula that the buoyancy force is related to the density of the liquid, the volume of liquid displaced by the object, and has nothing to do with the depth of immersion of the object.

Understanding and application of Archimedes' principle.

1. To understand the formula of Archimedes’ theorem, please note:

(1) The formula is the density of the liquid, not the density of the object immersed in the liquid.

(2) V discharge in the formula is the volume of liquid displaced when immersed in liquid. Objects can be fully immersed or partially immersed.

2. When calculating using Archimedes' principle, pay attention to the unity of units during the calculation process.

Buoyancy of water PPT, Part 5: The sinking and floating of objects

Discussion: A solid object is immersed in a liquid. Can you judge whether the object will float or sink based on the relationship between the density of the object and the density of the liquid?

Conclusion: ρ substance = ρ liquid suspension

ρ object>ρ liquid sinks

ρ substance <ρ liquid floats

Example: Boiling glutinous rice balls or dumplings; oil tanker leakage

Buoyancy of water PPT, Part 6: Application of floating and sinking conditions of objects

1. P25 experiment, Figure 1-50, principle of density meter

2. P25 Experiment, Figure 1-52, Principle of Steel Hulled Ship

3. P26 experiment, Figure 1-54, principle of submarine floating and sinking

Water buoyancy PPT, part 7: summary

1. The concept of buoyancy

2. Archimedes’ Principle

3. Floating and sinking conditions of objects:

(1) F floating > G, floating. The inevitable result of floating is floating.

(2) F float < G sink

(3) F float = G float

(4) Floating, F float = G

4. Methods learned to find buoyancy:

(1) Measurement method, F float = G - F pull

(2) Archimedes’ principle F float = G drain = ρ liquid g V drain

Water Buoyancy PPT, Part 8: Practice

1. Regarding the buoyancy force on an object immersed in a liquid, which of the following statements is incorrect? [ ]

A． The direction of buoyancy is vertically upward;

B. The force exerting buoyancy must be water;

C. The magnitude of the buoyant force is proportional to the mass of liquid displaced;

D. A solid iron ball can also float on the liquid surface.

2. After putting a wooden ball into the water to a certain depth by hand, release your hand and the wooden ball will float up. When the wooden ball does not come out of the water, which of the following statements is correct? [ ]

A. The gravity and buoyancy force on the wooden ball remain unchanged;

B. The gravity on the wooden ball remains unchanged and the buoyancy becomes larger;

C. The gravity and buoyancy of the wooden ball become smaller;

D. The gravity on the wooden ball remains unchanged and the buoyancy gradually becomes smaller.

3. The density of alcohol is 0.8×103 kg/m3. If an iron block with a volume of 500 cm3 is immersed in alcohol, the buoyant force it will experience is ______N.

4. An object with a volume of 1000 cm3 floats on the liquid surface, and the buoyant force it experiences is 3.92 N. Draw a schematic diagram of the force on the object, and find the density of the object. What material is this object made of?

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