"The Floating and Sinking Conditions and Applications of Objects" Buoyancy PPT Courseware 5

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"The Floating and Sinking Conditions and Applications of Objects" Buoyancy PPT Courseware 5

What exactly determines the sinking and floating of objects?

Experimental verification

Exploration process one: Put the vials and toothpaste skins on the experimental table into the water respectively, and observe their floating and sinking in the water.

What phenomenon was observed?

Exploration process two: Ask students to think of ways to change their ups and downs, and try to think about what methods you use to change their original ups and downs?

What was the original state of the vial and what method did you take to change its floating and sinking state?

What is the original state of the toothpaste skin, and what methods have you taken to change its floating and sinking.

When the volume of an object remains constant, the heavier the object, the easier it is to sink.

When the gravity of an object is constant, the larger the volume of the object, the greater the buoyant force it receives and the easier it is to float.

Classroom thinking: What are the similarities and differences between floating and levitation?

Common points:

Stand still under the influence of a balancing force.

For objects floating and suspended on the liquid surface, the buoyancy force is equal to gravity.

difference:

Floating is when part of an object is immersed in a liquid, and levitation is when the entire object is immersed in a liquid.

Think about what are the ways to change the floating and sinking of objects?

Change its own gravity.

Change its own volume or change the density of the liquid to change the buoyancy.

Standard practice questions:

1. Fill in the blanks:

1. For an object immersed in a liquid, when F>G, the object will ----------; when F

2. An object weighs 37 N in air and 12 N when immersed in water. The buoyant force on the object is ------------.

3. Submarines float and sink by changing ----------------. The balloon moves up and down by changing ------------------.

4. A wooden block floats on the water, and the volume submerged in the water is 3/5 of the total volume. Then the density of the wooden block is --------------------------.

5. When a ship sails from the river into the sea, gravity ---------, buoyancy ---------, and the volume of water displaced ---------.

6. The density meter is an instrument for measuring -------------. The buoyancy force it experiences when floating in different liquids is ----------. In liquids with higher density, The volume of liquid displaced in ---------, the deeper the glass tube is immersed under the liquid surface ---------.

2. Multiple choice questions:

1. A solid iron ball is placed in water, alcohol, and mercury respectively. The one that experiences the greatest buoyancy is ( )

A. Water B. Alcohol C. Mercury D. Unable to determine

2. A solid object with uniform density is suspended in water. If the object is cut into two pieces of different sizes and still placed in the water, then ( )

A. The big piece sinks and the small piece floats B. The big piece sinks and the small piece floats C. Both pieces float D. Both pieces float

3. There is a piece of ice floating on the water. When the ice completely melts, the scale on the water surface will be ( )

A. Increase B. Decline C. No change D. Unable to determine

4. There is a wooden boat in the pool filled with stones. After the stones are thrown into the pool water, the water surface will ( )

A. Increase B. Decline C. No change D. Unable to determine

ship

Working principle: The object floats on the water.

By making hollow steel that is denser than water, its average density is reduced, while more water is displaced and the available buoyancy is increased.

Ships are floating bodies in rivers and seas, so they experience the same buoyancy force, which is equal to the ship's own gravity. According to Archimedes' principle, its immersed volume in sea water is smaller than that in river water.

Ships always float on the water. When a ship sails from the river to the sea, the magnitude of the gravity it experiences is _______ (increases, decreases, remains the same); the magnitude of the buoyancy it experiences _______ (increases, decreases, changes). does not change); the volume of water it displaces _______ (gets bigger, gets smaller, does not change); does the ship sink more or float more?

submarine

Working principle: The submarine floats, dives and levitates by changing its own gravity.

The change in the submarine's dead weight depends on how much water is filled or released into the tank.

summary

1. Floating and sinking conditions of objects

When F floats < G object, the direction of the resultant force is vertically downward, and the object sinks.

When F float = G object, the resultant force is zero, that is, the two forces are balanced, and the object will float at this time.

When F float > G object, the direction of the resultant force is vertically upward, and the object floats up.

When an object floats, F float = G object.

2. Application of floating and sinking conditions

The principles of floating and sinking of ships, density meters, hot air balloons and submarines.

1. There is a solid object. In order to measure the density of the material that makes up it, hang it under a spring balance. The spring scale will read 19.6 N. Submerge it into water and weigh it. The spring balance will read 14.7 N. The object's The volume is _____ meters3 and the mass is _____ kilograms. From this we know that its density is _____.

2. If you are given a piece of ore, I will also give you a spring dynamometer, a glass of water and thin wire. Using the above equipment to conduct experiments and using relevant knowledge to perform calculations, we can determine the following of this ore:

A. Quality b. water buoyancy

C. Volume D. density

3. A solid metal ball with a volume of 200 cm3 is hung under the spring balance (the density of metal is 8×103 kg/m3). The spring balance indicates _____. When half of the ball is immersed in water, the ball is buoyant by _____N. At this time, the spring balance reads _____N.

4. There is an airship with a volume of 500 meters3. When it is stationary in the air near the ground, the buoyancy force of the air on it is _____ Newtons, and the airship's self-weight is _____ Newtons. (ρ air = 1.29 kg/m3)

5. Pull the iron block tied with a string from the water to the water surface at a constant speed (the iron block is not exposed to the water). During this process, the pulling force of the rope on the iron block is:

A. Gradually getting bigger B. gradually become smaller

C. Always the same D. Unable to judge

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Update Time: 2024-10-07

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