The international unit of mass is kilogram. Others are: ton, gram, mg, 1 ton =103kg =106g =109mg (output in thousands).

3. The mass of an object does not change with its shape, state, position and temperature.

4. Quality measuring tools: Balance is usually used to measure quality in the laboratory. The commonly used balances are tray balance and physical balance.

5. Correct use of the balance: (1) Put the balance on a horizontal platform and put the stray code on the zero line at the left end of the balance; (2) Adjust the balance nut so that the pointer is on the center line of the dial, and then balance the balance; (3) Place the object on the left plate, add and subtract weights on the right plate with tweezers and adjust the position of the walking code on the scale until the beam is balanced; (4) At this time, the mass of the object is equal to the total mass of the weight in the right plate plus the scale value of the stray code.

6. When using Tianping, it should be noted that (1) cannot exceed the maximum weighing; (2) Add and subtract heavy objects with tweezers, and the movements should be light; (3) Don't put wet objects and chemicals directly on the tray.

7. Density: The mass per unit volume of a substance is called the density of this substance. ρ means density, m means mass and v means volume. The formula for calculating the density is: the density unit is kg/m3 (that is, g/cm3),1g/cm3 =1000 kg/m3; The unit of mass m is: kg; The unit of volume v is m 3.

8. Density is a characteristic of matter, and the density of different kinds of matter is generally different.

9. The density of water ρ = 1.0× 103kg/m3.

10. Application of density knowledge: (1) Identification of substances: Measure the mass m with a balance, measure the volume v with a measuring cylinder, and work out the density of substances according to the formula. Check the densitometer again. (2) Find the mass: m = ρ v. (3) Find the volume:

1 1. Physical properties of substances include: state, hardness, density, specific heat, light transmittance, thermal conductivity, electrical conductivity, magnetism, elasticity, etc.

Chapter 7 From Particles to the Universe

1. The content of molecular dynamics theory is: (1) Matter is composed of molecules with gaps between them; (2) The molecules of all objects do random motion endlessly; (3) There is attraction and repulsion between molecules.

2. Diffusion: the phenomenon that different substances contact and enter each other.

3. When solid and liquid are compressed, the repulsion between molecules is greater than gravity.

Solids are difficult to elongate because the attraction between molecules is greater than the repulsion.

4. Molecules are composed of atoms, and atoms are composed of nuclear and extranuclear electrons.

The nucleus consists of protons and neutrons.

5. Thomson discovered electrons (1897); Rutherford discovered protons (1919); Neutron discovered in chadwick (1932); Gherman put forward the quark hypothesis (196 1 year).

6. Accelerator is a powerful weapon to explore tiny particles.

7. The Milky Way is a huge celestial system composed of stars and diffuse matter, and the sun is just one of ordinary stars.

8. The universe is a hierarchical celestial structure system. Most scientists believe that the universe was born in a big bang 654.38+0.5 billion years ago. This explosion is a whole, involving all matter, time and space in the universe. The explosion caused the universe to expand everywhere, and the temperature dropped accordingly.

9. 1 AU (astronomical unit) refers to the distance from the earth to the sun.

10.y. (light years) refers to the distance that light travels in a vacuum for one year.

Chapter VIII Induction of Electric Power Knowledge

1. What is force? Force is the action of an object on an object.

2. The forces between objects are mutual. When an object exerts a force on another object, it is also subjected to the force exerted on it by the latter.

3. Function of force: Force can change the motion state of an object and also change its shape. (The change of the shape or volume of an object is called deformation. The unit of force is Newton (abbreviation: cow). Coincidentally, n. 1 Newton is about the force you use to pick up two eggs.

The tool for measuring force in the laboratory is a spring dynamometer.

6. Principle of spring dynamometer: Within the elastic limit, the elongation of the spring is directly proportional to the tensile force.

7. How to use the spring dynamometer: (1) Check whether the pointer is at zero scale, and if not, set it to zero; (2) Identify the minimum scale and measuring range; (3) Gently pull the scale hook several times to see whether the pointer returns to zero scale after each release; (4) When measuring, the axis of the spring in the spring dynamometer is consistent with the direction of the measured force; 5] When observing the reading, the line of sight must be perpendicular to the dial. (6) Force measurement shall not exceed the range of the spring dynamometer.

8. The three elements of force are: the size, direction and action point of force, which are called the three elements of force, and they can all affect the action effect.

9. The schematic diagram of force is represented by line segments with arrows. The specific painting method is:

(1) uses the starting point of the line segment to indicate the stress point;

(2) Draw a line segment with an arrow in the direction where the force extends, and the direction of the arrow indicates the direction of the force;

(3) If there are several forces in the same picture, the greater the force, the longer the line segment should be. Sometimes, it can also be displayed in the force diagram,

10. Gravity: The force exerted by an object close to the ground due to the gravity of the earth is called gravity. The direction of gravity is always vertical downward.

1 1. Calculation formula of gravity: G=mg (where g is the ratio of gravity to mass: g=9.8 Newton/kg, and g= 10 Newton/kg can also be used for rough calculation); Gravity is proportional to mass.

12. The thick vertical line is made according to the principle that the gravity direction is always vertical downward.

13. center of gravity: the center of gravity acting on an object is called the center of gravity.

14. Friction: When two objects that are in contact with each other are about to move or have moved relative to each other, a force that hinders the relative movement will be generated on the contact surface. This force is called friction.

15. Sliding friction is related to the roughness and pressure of the contact surface. The greater the pressure, the rougher the contact surface and the greater the sliding friction.

16. Method of increasing beneficial friction: increase pressure to make the contact surface rough.

Methods to reduce harmful friction: (1) make the contact surface smooth and reduce the pressure; (2) Use rolling instead of sliding; (3) adding lubricating oil; (4) Use an air cushion. (5) let the object out of contact (such as maglev train).

Chapter 9 pressure and buoyancy knowledge induction

1. pressure: the force acting vertically on the surface of an object is called pressure.

2. Pressure: The pressure per unit area of an object is called pressure.

3. Pressure formula: P=F/S, where the unit of p is Pascal, abbreviated as Pa, 1 Pa = 1 N/m2, and the unit of pressure f is cattle; The unit of stress area s is m2.

4. supercharging method: (1)S remains unchanged, f =；; (2)F is a constant, and S↓ (3) simultaneously puts F = and S↓. The method of decompression is the opposite.

5. The reason of liquid pressure: It is because the liquid is acted by gravity.

6. Characteristics of liquid pressure: (1) liquid has pressure on the bottom and wall of the container, (2) liquid has pressure in all directions; (3) The pressure of liquid increases with the increase of depth, and at the same depth, the pressure of liquid in all directions is equal; (4) The pressure of different liquids is also related to the density.

7.* Calculation formula of liquid pressure: (ρ is the density of liquid in kg/m3; g = 9.8n/kg； H is the depth, which refers to the vertical distance from the free surface of the liquid to a point inside the liquid, in meters. )

8. According to the formula of liquid pressure, it can be concluded that the liquid pressure is related to the density and depth of the liquid, but not to the volume and quality of the liquid.

9. The experiment that proves the existence of atmospheric pressure is the Madeborg Hemisphere Experiment.

10. Causes of atmospheric pressure: Air is produced by gravity, and atmospheric pressure decreases with the increase of height.

1 1. The experiment of measuring atmospheric pressure is: Torricelli experiment.

12. The instrument for measuring atmospheric pressure is a barometer. Common barometers are mercury barometer and empty box barometer (metal box barometer). 13. Standard atmospheric pressure: put in an atmospheric pressure equal to 760mmhg. 1 standard atmospheric pressure = 760mmhg =1.013x105pa =10.34m H2O.

14. Relationship between boiling point and air pressure: The boiling point of all liquids decreases when the air pressure decreases and increases when the air pressure increases.

15. Relationship between fluid pressure and flow rate: the greater the flow rate, the smaller the pressure; The slower the speed, the greater the pressure.

1. Buoyancy: All objects immersed in liquid are subjected to vertical upward force of liquid, which is called buoyancy. The buoyancy direction is always vertical. (Objects are also affected by buoyancy in air.)

2. Conditions of ups and downs of objects: (Immersed in liquid at first)

Method 1: (Specific gravity and buoyancy of objects)

(1)F floats < g and sinks; (2)F floating >; G, floating (3)F floating = G, floating or floating.

Method 2: (Compare the densities of objects and liquids)

(1) F floats < g and sinks; (2) F floating >; G, floating (3) F floating = G, suspended. (Will not float)

3. Causes of buoyancy: Objects immersed in liquid are subjected to upward and downward pressure difference of liquid.

4. Archimedes principle: An object immersed in a liquid is subjected to upward buoyancy, and the buoyancy is equal to the gravity of the liquid it displaces. The buoyancy of an object immersed in a gas is equal to the gravity it receives when it displaces the gas.

5. Archimedes principle formula:

6. Buoyancy calculation methods are:

(1) weighing method: f float = g-f, (g is the gravity of the object, and f is the reading of the spring balance when the object is immersed in liquid).

(2) Differential pressure method: F float =F up -F down.

(3) Archimedes principle:

(4) Balance method: F floating =G object (applicable to floating and suspension)

7. Buoyancy utilization

(1) Ship: It is made of hollow material with density greater than water, so that more water can be discharged. This is the reason for shipbuilding.

(2) Submarine: change its own gravity to achieve ups and downs.

(3) Balloons and airships: filled with gas with density less than air.

Chapter 10 Induction of Force and Sports Knowledge

1. Newton's first law: When no external force acts on all objects, they always remain stationary or move in a straight line at a uniform speed. Newton's first law is further deduced on the basis of empirical facts, so it can't be proved by experiments.

2. Inertia: The property that an object keeps its state of motion unchanged is called inertia. Newton's first law is also called the law of inertia.

3. The state of balance of an object: When an object is acted by several forces, we say that these forces are in a state of balance if it stays still or moves in a straight line at a constant speed. When an object is in equilibrium under the action of two forces, it is called two-force equilibrium.

4. Conditions for the balance of two forces: If the two forces acting on the same object are equal in magnitude and opposite in direction, the resultant force when the two forces are balanced on the same straight line is zero.

5. An object will remain stationary or move in a straight line at a constant speed without force or balance force.

I hope you can adopt it.