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MindMap Gallery Some physics knowledge points for junior high school students
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Some physics knowledge points for junior high school students
It involves mass, density, force and motion, pressure, buoyancy, work and mechanical energy. The introduction is detailed and the knowledge is comprehensive. I hope it can be helpful to everyone!
Edited at 2024-03-13 21:38:15- bacteria
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.
- Plant asexual reproduction
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.
- Reproductive development of animals
This is a mind map about the reproductive development of animals, and its main contents include: insects, frogs, birds, sexual reproduction, and asexual reproduction. The summary is comprehensive and meticulous, suitable as review materials.
Some physics knowledge points for junior high school students
- bacteria
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.
- Plant asexual reproduction
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.
- Reproductive development of animals
This is a mind map about the reproductive development of animals, and its main contents include: insects, frogs, birds, sexual reproduction, and asexual reproduction. The summary is comprehensive and meticulous, suitable as review materials.
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- Outline
physics
quality
Mass is a fundamental property of objects. It does not change with changes in the shape, state and position of the object
Represented by the letter m
Definition: How much matter an object contains
Quality measurement: Commonly used tools for measuring quality include steelyard scales, case scales, bench scales, electronic scales, balances, etc. Laboratory balance with pallet to measure mass
Using a balance: six steps
Pay attention to the range
Tweezers
left thing right code
measuring cylinder
Recognize, read and memorize
Note: When reading, the line of sight is flush with the lowest part of the concave liquid surface.
Conversion
1 t= 1*10^6 g 1 kg = 1*10^3 g 1 mg = 1*10^3 g
density
Definition of density: The mass of a certain substance per unit volume is called the density of the substance
Definition formula: P=m/v (not a determinant, density is a characteristic of matter)
Density measurement: Use a balance to measure the mass of a liquid, and use a graduated cylinder to measure the volume of the liquid. Find density using density formula
special method measurement
Equipment: stones, beakers, balances and weights, enough water, thin wire (1) Use the adjusted balance to measure the mass of the solid to be measured (2) Fill the beaker with water, use the balance to measure the beaker and water (3) Use a thin wire to pull the stone and immerse it in the beaker. After the liquid overflows, use a balance to measure the total mass of the beaker at this time.
Equipment: Beaker, enough water, enough liquid to be measured, balance and weights: (1) Use the adjusted balance to measure the mass of the empty beaker (2) Fill the beaker with water, use the balance to measure the mass of the beaker and The mass of water is (3) Empty the water in the beaker, and then fill the beaker with the liquid to be measured. The mass of the beaker and liquid is measured at this time.
Equipment: measuring cylinder, solid to be measured, water, thin wire (1) Put appropriate amount of water into the measuring cylinder and read the time (2) Put the solid to be measured into the water in the measuring cylinder and read the time (3) Use a pin to press the object completely into the water and read the reading.
force and motion
Common forces: gravity, friction, elasticity, buoyancy
force effect
Can change the shape of objects
Can change the motion state of an object
Represented by the letter N
How force is measured: spring dynamometer
Three elements of force: magnitude, direction, and point of action
Force analysis diagram
inertia
Definition: The property of an object that remains in motion is called inertia
Note: Inertia is a property of an object. All objects always have inertia
Two force balance
Definition: When an object is acted upon by two forces, if it can maintain a state of rest or a state of uniform linear motion, it is called a two-force balance.
Conditions: Two forces act on the same object, are equal in magnitude, opposite in direction, and in a straight line
pressure
Definition: The pressure exerted on an object per unit area is called pressure
Physical meaning: Pressure is a physical quantity that expresses the effect of pressure
Formula: p=F/s
Methods to increase or decrease pressure: change the size of the pressure, change the size of the stressed area
liquid pressure
The reason for the pressure inside the liquid: the liquid is gravity and fluid
Liquid pressure characteristics
⑴There is pressure in all directions inside the liquid
⑵ At the same depth, the pressure in all directions is equal
⑶ As the depth increases, the pressure of the liquid increases
⑷The pressure of a liquid is related to the density of the liquid. When the depth is the same, the greater the density of the liquid, the greater the pressure.
Calculation formula: ρ*g*h
Connector
⑴Definition: A container with an open upper end and a connected lower part
⑵Principle: When the connector is filled with a liquid and the liquid does not flow, the liquid levels in each container remain equal.
⑶Application: teapot, boiler water level gauge, ship lock
Atmospheric pressure: Torricelli experiment
The relationship between gas pressure and flow rate: In gases and liquids, the greater the flow rate, the smaller the pressure.
buoyancy
Archimedes' Principle: The buoyant force on an object immersed in a liquid is equal to the gravitational force on the liquid it displaces.
Formula: F float = G row = ρ liquid V row g
Applications of buoyancy: ships, submarines
Object sinking and floating conditions
F float>g object: float
F float=g substance: suspended
FFloating<g: sinking
work and mechanical energy
work and power
achievement
Definition: If a force acts on an object and the object moves a certain distance in the direction of the force, in mechanics it is said that the force has done work.
There are two necessary factors for workmanship: one is the force acting on the object, and the other is the distance the object moves in the direction of the force.
The product of a force and the distance moved in the direction of the force is called work
Formula: W=FS
power
In the same time, the more work done, the greater the physical power
Formula: P=W/t or P=Fv
Represented by W
Mechanical energy
Definition: Kinetic energy and potential energy are collectively called mechanical energy (conservation of mechanical energy)
Kinetic energy: The energy an object possesses due to motion is called kinetic energy
For objects with the same mass, the greater their moving speed, the greater their kinetic energy; for objects moving at the same speed, the greater their mass, the greater their kinetic energy
potential energy
Gravitational potential energy: The energy an object has due to its height position
The higher an object is lifted, the greater its mass and the greater its gravitational potential energy.
Elastic potential energy: the energy an object has due to elastic deformation
The greater the elastic deformation of an object, the greater its elastic potential energy.
⑴ Experimental process: Fill a glass tube about 1m long with one end closed with mercury, plug the mouth of the tube, and then insert it upside down in the mercury tank and release the finger that blocked the mouth of the tube. The mercury level in the tube will stop falling if it drops a little. At this time, the height difference between the inner and outer mercury surfaces of the tube is approximately 760mm. ⑵ Principle analysis: Take a liquid piece in the tube where it is level with the liquid surface outside the tube. Because the liquid does not move, the liquid piece is balanced by the pressure above and below. That is, the upward atmospheric pressure = the pressure generated by the mercury column.
Force conditions of the object Motion state of the object Description
Force is not what creates or maintains motion. Force is what changes the state of motion of an object.
The force causes the spring to elastically deform