"Conditions for Floating and Sinking of Objects" Pressure and Buoyancy PPT Courseware

Description

"Conditions for Floating and Sinking of Objects" Pressure and Buoyancy PPT Courseware

Observe and think

1. Why does a wooden block submerged in water float upward?

2. Why does an iron block immersed in water sink to the bottom of a container?

3． Why can ships made of steel sail on the sea?

4. Objects in liquids all experience buoyancy. Why do some float, some sink, and some float?

1. Floating and sinking conditions of objects

1. The relationship between buoyancy and gravity

Put the wooden block and the iron block into the water respectively, observe the direction of their movement after letting go, and try to analyze the reasons.

When F float > G, the net force is upward and the object floats up.

When F float < G, the net force is downward and the object sinks.

When F float = G, the net force is zero and the object is suspended in the water.

2. The relationship between the density of objects and the density of liquids

Research conditions: A solid object is immersed in a liquid and is subject to gravity and buoyancy.

Buoyancy: F float = ρ liquid gV displacement; Gravity: G = ρ object g V object;

V row = V thing

Compare based on floating and sinking conditions:

F float > G float: ρ liquid > ρ matter

F float = G suspension: ρ liquid = ρ substance

F float＜G sink: ρ liquid＜ρ matter

Floating: ρ liquid > ρ object

3． Discussion of floating and sinking conditions

(1) Floating and sinking are unbalanced states; suspension and floating are equilibrium (stationary) states.

(2) Floating, sinking and suspending: row V = V; floating: row V < V

(3) When using floating and sinking conditions for hollow objects, the average density of the object, ρ, can be compared with the density of the liquid, ρ.

think

A nut sinks in the water, but why can a warship much larger than the nut float on the water?

Experimental exploration

Archimedes' principle:

The buoyant force on an object is equal to the gravitational force on the liquid displaced by the object.

Experimental results

To make objects that can float on the water out of materials that are denser than water, you can make the objects hollow to increase the volume they can displace liquid and increase their buoyancy.

2. Application of buoyancy

Think about it, do it

Use plasticine to make a boat that can carry heavy loads and make it float on the water.

ship

(1) Working principle: Making steel into a hollow ship can displace more water and float on the water.

(2) Displacement (m displacement): the mass of water displaced when the ship is fully loaded: F float = m displacement g and F float = G

∴ m ship + m cargo = m row

(3) Load line

submarine

Simulated submarine: Use a syringe to inject into the sealed bottle, drain the water in the bottle, and the bottle floats upwards

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

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,

∵ ρ seawater > ρ seawater , ∴ V row > V′ row

Example 3: An object weighing 15 N spilled 5×10-4 m3 of water after being immersed in a container filled with water. Then this object is ( )

A. Float on the water b. sink to the bottom

C. Suspended in water D. All of the above situations are possible

【Analysis】

According to Archimedes' principle

Ffloat = ρwater gVdischarge

=1.0 ×103 kg/m3 ×9.8 N/kg×5×10-4 m3

=4.9 N<15 N

∵ F floats

Operation

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

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For more information about the "Pressure and Buoyancy Conditions of Floating and Sinking Objects" PPT courseware, please click the "Pressure and Buoyancy ppt Floating and Sinking Conditions of Objects ppt" tag.

"Studying the Floating and Sinking Conditions of Objects" Buoyancy and Lift PPT Courseware 2:

"Studying the Floating and Sinking Conditions of Objects" Buoyancy and Lift PPT Courseware 2 Learning Objectives: 1. Through experiments, explore the floating and sinking conditions of objects; 2. Use the floating and sinking conditions of objects to explain the floating and sinking principles of submarines and balloons and the salvage method of buoys. What are the conditions for the floating and sinking of objects?

"Studying the Floating and Sinking Conditions of Objects" Buoyancy and Lift PPT Courseware:

"Studying the Floating and Sinking Conditions of Objects" Buoyancy and Lift PPT courseware Review the past and learn new things 1. What factors are related to the size of buoyancy? Liquid, V displacement 2. What is the relationship between the size of buoyancy and the weight of liquid displaced by an object? F float = G row 3. How to calculate the gravity of an object? G=mg=gV 4..

"Conditions of Floating and Sinking of Objects" Pressure and Buoyancy PPT Courseware 2:

"Conditions of Floating and Sinking of Objects" Pressure and Buoyancy PPT Courseware 2 Method classification: 1. Change the buoyancy under certain circumstances of gravity (that is, change the P liquid and V discharge). For example, the V row can be changed by ships, etc., and the density can be changed by selection. 2. Buoyancy (volume remains unchanged) changes under certain circumstances..

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Update Time: 2024-11-22

This template belongs to Physics courseware Beijing Normal University eighth grade physics volume 2 industry PPT template

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