"Buoyancy" PPT courseware 4

Description

"Buoyancy" PPT courseware 4

When an empty mineral water bottle with a tight cap is pressed into the water, your hand will clearly feel the upward force of the water on the bottle.

After releasing the bottle, the bottle will rise upwards out of the water

Think about it: Does an iron block that sinks when placed in water also experience buoyancy? How to verify?

When an object is placed in water, it will sink and the force gauge reading will become smaller. Why?

An iron block that sinks when placed in water also experiences buoyancy.

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

2. Make a diagram of the buoyancy force on the object in the figure below.

Feedback exercise one

1. A 1N hook code is hung on the spring dynamometer hook. When the hook code is immersed in water, the spring dynamometer indicates 0.87N. The buoyancy force on this hook code is ( ) N.

2. There is an iron ball hanging under the spring dynamometer. When it is at rest, the reading of the spring dynamometer is 21.9N. When the iron ball is immersed in water, the buoyancy force on the iron ball is 4.9N. At this time, the spring dynamometer's reading is 21.9N. The number shown is ( )N.

Explore:

1. What factors are related to the size of buoyancy?

2. Conjecture:

①It may be related to the density of the liquid

②It may be related to the volume of the object immersed in the liquid

③It may be related to the depth of the object immersed in the liquid

3. Design experiments:

Notice:

(1) When the object is completely immersed, the size of the buoyancy force has nothing to do with the depth of the liquid.

(2) Row V represents the volume of liquid displaced by an object.

When the object is completely immersed in the liquid, then V = V

When only part of the object is immersed in the liquid, then V discharge < V object

(3) The law also applies to gases (the buoyancy force is equal to the gravitational force on the gas it displaces)

Feedback exercise two

1. An object with a mass of 0.3kg is completely immersed in a container filled with water. The overflowing water is 100g. Then the buoyancy force on the object is ( ) N. (g=10N/Kg)

2. When a stone sinks in a liquid, it is affected by the buoyancy force (fill in "received" and "not affected"). If a stone weighs 5N, hang the stone at the bottom of the spring dynamometer and immerse it in a certain In this liquid, the spring force gauge indicates 2N, and the buoyancy force exerted by the liquid on the stone is __3__N. From this we can see that the liquid displaced by this stone weighs __3__N.

Consolidation exercises

1. Iron blocks A and B are of the same weight. A is immersed in water and B is immersed in kerosene. The buoyant force on the _____ iron block is greater.

2. Four spheres A, B, C, and D have the same shape and volume but different materials. They are at rest in water as shown in the figure. Among them, the one with the smallest buoyancy force is ( )

A.A B.B C.C D.D

Variation 1: As shown in the picture, when the ball floats from under the water to floating on the water, the correct judgment is (B)

A. Before emerging from the water, the buoyancy gradually increases; after emerging from the water, the buoyancy continues to increase.

B. Before emerging from the water, the buoyancy remains unchanged

C. Before emerging from the water, the buoyancy gradually decreases

D. Before emerging from the water, the buoyancy remains unchanged; after emerging from the water, the buoyancy begins to gradually increase.

Deformation 2: Solid iron balls, wooden balls and copper balls of equal mass are placed in a container with enough water to completely penetrate the water. When the three balls are stationary, the buoyancy force they receive is (C)

A. The iron ball has the greatest buoyancy force. B. The copper ball has the greatest buoyancy force.

C. The wooden ball has the largest buoyant force. D. The three balls have the same buoyant force.

As shown in the figure, an iron bucket and a solid iron ball with equal masses tied to the end of the rope are immersed in water at the same time and rest at the position shown in the figure. The relationship between the pulling forces F1 and F2 of the rope on them is: ( )

A. F1> F2 B. F1＝F2 C. F1< F2 D. Unable to determine

Keywords: buoyancy teaching courseware, New People's Education Edition eighth grade physics PPT courseware volume 2, eighth grade physics slide courseware download, buoyancy PPT courseware download, .ppt format

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Update Time: 2024-08-03

This template belongs to Physics courseware People's Education Edition Physics for Grade 8, Volume 2 industry PPT template

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