MindMap Gallery buoyancy
Buoyancy includes buoyancy preparation, buoyancy basics, sinking and floating conditions, buoyancy calculations, liquid level changes, and buoyancy applications. I hope this mind map will be helpful to you.
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This is a mind map about bacteria, and its main contents include: overview, morphology, types, structure, reproduction, distribution, application, and expansion. The summary is comprehensive and meticulous, suitable as review materials.
This is a mind map about plant asexual reproduction, and its main contents include: concept, spore reproduction, vegetative reproduction, tissue culture, and buds. The summary is comprehensive and meticulous, suitable as review materials.
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buoyancy
Buoyancy preparation
density
Definition: The mass of a certain substance per unit volume is called the density of the substance, usually represented by the Greek symbol ρ
Features: Density is a characteristic of matter. It is only related to the type and state of the matter, and has nothing to do with other factors such as mass, volume, shape, state of motion, etc.
Formula and unit: ρ=m/v, the unit of density in the International System of Units is: kg/m³, the common unit is: g/cm³,
Applications and calculations:
①Identify substances: Find the density of the object to be measured based on the conditions set in the question, and then compare the calculated value with the density table to determine the type of substance.
②Proportion problem: Known mass, density, volume, the multiple relationship or proportional relationship between certain physical quantities, solving the ratio of unknown quantities, etc.
③Hollow problem: including two cases of judging whether an object is hollow or solid and calculating the volume of the hollow part; to judge whether it is hollow or solid, you can use any of the three methods of comparing density, comparing volume, and comparing mass; calculating the hollow part When it comes to partial volume, the volume of the material that makes up the object must be found. V space = V total - V material
④Average density: ρ=Mtotal/VTotal. The total mass of the mixture is equal to the sum of the masses of the various substances. Without considering the volume change after the substances are mixed, the volume of the mixture is equal to the sum of the volumes of the individual substances.
pressure
Definition: Pressure = pressure/forced area, that is, p=F/S, applicable to solids, gases and liquids
Note: F is pressure, not gravity; S is the force-bearing area, not the surface area or base area of the object
Unit: Pascal, symbol Pa, 1Pa=1N/㎡
liquid pressure
Cause: Produced by the gravity of the liquid, and the liquid is fluid
Characteristics of liquid pressure:
①The liquid exerts pressure on the bottom and side walls of the container, which increases with depth.
② There is pressure in all directions inside the liquid, and at the same depth, the pressure in all directions is equal
③Liquid pressure is related to the density of the liquid. At the same depth, the greater the density of the liquid, the greater the pressure.
④ Liquid pressure formula: p = ρ liquid gh, where ρ liquid represents the density of the liquid, h represents the depth, that is, the vertical distance from the desired pressure point to the free liquid surface.
Liquid pressure and pressure analysis of cylindrical containers:
The pressure of the liquid on the bottom of the container: F=pS= ρ liquid hs=G liquid
The pressure of the liquid on the bottom of the container: p=ρ liquid gh or p=G liquid/S
buoyancy basis
buoyancy
Concept: An object immersed in a liquid (or gas) is affected by the liquid (or gas).
cause
Imagine a cube submerged in water, with water pressure acting on all six surfaces. The pressure on the left and right sides is the same and opposite in direction. It is a pair of balancing forces. In the same way, the pressure on the front and rear sides is also a pair of balancing forces. Due to the difference in depth, the pressure on the lower surface is greater than the upper surface, so a force is generated
Note: When the lower surface of the columnar body immersed in the liquid is in close contact with the bottom of the container, the upward pressure of the liquid on the object is zero. The object will not be affected by buoyancy, such as a bridge pier in the water.
Direction: vertically upward
Measurement of buoyancy:
Using a spring dynamometer
① Use a spring dynamometer to measure the gravity of the object G=F1
②Immerse the object in water and record the spring dynamometer indication F2
③Carry out force analysis on the object: F float = F1-F2
Sink and float conditions
Basic idea: Objects in liquid are affected by gravity and buoyancy at the same time, and their storage conditions depend on the relationship between gravity and buoyancy.
Different states of objects in liquids
Floating: F float > G ρ liquid < ρ matter
Floating: F float = G ρ liquid > ρ object
Suspension: F float = G ρ liquid = ρ substance
Sinking: F float<G ρ liquid<ρ object
Sinking to the bottom: F branch F float = G ρ liquid < ρ object
Buoyancy calculation
Archimedes' principle method:
Formula: F float = G drain = ρ liquid gV drain
pressure difference method
F float = ρ liquid gh lower surface - ρ liquid gh lower surface
h surface refers to the distance from the surface to the free liquid surface
Weighing method
F float=G object-F
F refers to the reading of the spring force gauge when the object is immersed in water.
equilibrium state method
F float = G object (floating, suspended)
proportional method
Floating: F float = G substance, that is, ρ liquid gV drainage = ρ substance gV substance, the proportional formula can be formulated as ρ substance/ρ liquid = V drainage/V substance
Immersion: G substance = ρ substance gV substance, F float = ρ liquid gV liquid drain, and V drain liquid = V substance. Comparing the two formulas, we can get: ρ substance/ρ liquid = G substance/F float
Liquid level change problem
ρ liquid = ρ water
Liquid level remains unchanged
ρ liquid>ρ water
Liquid level rises
ρ liquid<ρ water
Liquid level drops
Buoyancy applications
density meter
principle
When the object is floating, G=F float = ρ liquid gV discharge. The density of the liquid is different due to the different immersion depth of the density meter.
The same density meter floats in different liquids, and the buoyancy forces it experiences are all equal.
Features
Density meter does not have 0 scale mark
The upper reading of the density meter is small, and the lower reading is large.
The density meter scale is uneven, sparse at the top and dense at the bottom.
ship
principle
Making steel into a hollow ship can displace more water and gain more buoyancy to float on the water.
waterline
The "draft" allowed for a ship to be fully loaded in different waters and seasons
Displacement
Quality of water discharged by ships
Derived formula
V drain =m/ρ liquid
G discharge=mg
F float=mg
G total=mg
Ups and downs other applications
submarine
By changing its own gravity, that is, the drainage and water inflow of the water tank, it achieves floating up and down.