"Utilization of Buoyancy" Buoyancy PPT courseware

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"Utilization of Buoyancy" Buoyancy PPT courseware

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During the Three Kingdoms period, there was "Cao Chong called Xiang".

In addition to using boats to weigh things, using boats to lift weights is also a Chinese invention. According to historical records, Huai Bing, a monk from Zhending County, once "salvaged iron oxen". He invented the buoyant lifting method.

learning target

(1) Know the principles of floating and sinking of ships, submarines, balloons, airships and density meters.

(2) Be able to use floating and sinking conditions to explain some simple problems.

1. From canoe to wooden boat

The principle of wooden boats: using the "hollow" method to increase buoyancy

The most modern ships also use this ancient method.

2. The invention of the steamship

Observation and Experimentation

Can plasticine float on water?

If you put the plasticine into pieces and put it into water, will it float on the water?

If you make it into a hollow object and put it into water, will it sink underwater?

Why does plasticine float?

F float 1

When hollow, the volume of displaced liquid increases

F float 2=G float

3. The ups and downs of the submarine

Simulate a submarine: Use a syringe to inflate the sealed bottle to drain the water in the bottle and make the bottle float upwards.

Working principle: It floats and dives by changing its own gravity.

4. Application of balloons and airships

Working principle: lift off by air buoyancy

Example analysis

Example 1 Regarding buoyancy, which of the following statements is correct ( )

A. A floating object must experience a greater buoyant force than a sinking object.

B. Objects sinking at the bottom of the container must not be buoyant

C. Objects floating in water may be suspended in kerosene

D. The deeper an object is submerged in the water, the greater the buoyant force it will experience.

Example 2 A ship sails from the sea into a river. The gravity it experiences is ______, the buoyancy force it experiences is ______; the volume of water it displaces is ______. (Fill in to get bigger, smaller or the same)

【Analysis】

The ship floats on the sea, F float = G;

It sails into the river and floats on the river: F′ float = G.

∵ G remains unchanged, ∴ F floats unchanged:

F float = F′ float

ρ sea water g V row = ρ sea water g V′ row,

∵ ρsea water > ρsea water ,

∴ V row > V′ row

Summary of this lesson

What did you gain from studying this class?

1. The invention of the steamship

Use the "hollow" method to increase buoyancy

2. Application of buoyancy

Submarines, balloons and airships, density meters

Practice in class

1. Using the same density meter to measure the density of different liquids, which of the following statements is correct ( )

A The higher the density meter floats, the greater the buoyancy force it experiences.

B Density meters float in different liquids, and the buoyancy forces they experience are all equal.

C The larger the displacement volume of the density meter, the greater the density of the liquid.

D The higher the density meter floats, the denser the liquid.

2. When a solid aluminum ball and an iron ball of equal mass are placed in water, the buoyant force on the iron ball _____ the buoyant force on the aluminum ball; if they are placed in mercury at rest, the buoyant force on the iron ball _____ buoyancy (optional ">", "<", "=")

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Update Time: 2024-09-10

This template belongs to Physics courseware Lu Jiao Edition Eighth Grade Physics Volume 2 industry PPT template

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