First, the motion of the particle (1)- linear motion

1) moving in a straight line at a uniform speed

1. average speed Vping =S/t (definition) 2. Useful inference vt 2-VO 2 = 2as.

3. Intermediate speed vt/2 = Vping =(Vt+Vo)/2 4. Final speed Vt=Vo+at.

5. Intermediate position speed vs/2 = [(VO 2+vt 2)/2] 1/26. Displacement S= V level T = VOT+at 2/2 = vt/2t.

7. Acceleration a=(Vt-Vo)/t With Vo as the positive direction, A and Vo are in the same direction (accelerating) a>0; On the other hand, a < 0

8. It is inferred experimentally that δs = at 2δs is the displacement difference of adjacent consecutive equal time (t).

9. Main physical quantity and unit: initial velocity (Vo):m/s

Acceleration (a): m/s 2 Final speed (Vt): m/s.

Time (t): second (s) Displacement (s): meter (m) Distance: meter speed unit conversion:1m/s = 3.6 km/h.

Note: (1) Average speed is vector. (2) The acceleration is not necessarily high when the speed of the object is high. (3)a=(Vt-Vo)/t is only a measure, not a judgment. (4) Other related contents: particle/displacement and distance /S-T diagram /V-T diagram/velocity and rate/

2) Free fall

1. Initial speed Vo=0

2. Final speed Vt=gt

3. Falling height h = gt 2/2 (calculated downward from Vo position) 4. Inference vt 2 = 2gh.

Note: (1) Free falling body is a uniformly accelerated linear motion with zero initial velocity, which follows the law of uniformly variable linear motion.

(2) A = G = 9.8 m/s 2 ≈ 10 m/s 2。 The acceleration of gravity is smaller near the equator, smaller than the flat in high mountains, and the direction is vertical downward.

3) Throw vertically upwards

1. displacement s = vote-gt 2/22. The final speed Vt= Vo- gt (g=9.8≈ 10m/s2).

3. It is useful to infer that vt 2–VO 2 =-2gs4. Maximum rising height hm = VO 2/2g (from the throwing point).

5. Round trip time t=2Vo/g (time from throwing back to original position)

Note: (1) Full-course treatment: it is linear motion with uniform deceleration, with positive upward direction and negative acceleration. (2) Sectional treatment: the upward movement is uniform deceleration, and the downward movement is free fall, which is symmetrical. (3) The process of ascending and descending is symmetrical, for example, at the same point, the speed is equal and the direction is opposite.

Second, the movement of particles (2)-curve motion gravity

1) flat throwing motion

1. horizontal velocity Vx= Vo 2. Vertical speed Vy=gt.

3. horizontal displacement Sx= Vot 4. Vertical displacement (sy) = gt 2/2.

5. Exercise time t=(2Sy/g) 1/2 (usually expressed as (2h/g) 1/2).

6. Closing speed vt = (VX 2+vy 2)1/2 = [VO 2+(gt) 2]1/2.

The angle β between the closing speed direction and the horizontal plane: tgβ = vy/VX = gt/vo.

7. Synthetic displacement S = (SX 2+SY 2) 1/2,

The included angle α between the displacement direction and the horizontal plane: tgα = sy/sx = gt/2vo.

Note: (1) Flat throwing motion is a curve motion with uniform change, with acceleration of g, which can usually be regarded as the synthesis of uniform linear motion in horizontal direction and free falling motion in vertical direction. (2) The movement time is determined by the falling height h(Sy) and has nothing to do with the horizontal throwing speed. (3) The relationship between θ and β is tgβ=2tgα. (4) Time t is the key to solving the problem of flat throwing. (5) An object moving along a curve must have acceleration. When the direction of velocity and the direction of resultant force (acceleration) are not in a straight line, the object moves in a curve.

2) Uniform circular motion

1. linear velocity V=s/t=2πR/T 2. Angular velocity ω = φ/t = 2π/t = 2π f.

3. centripetal acceleration a = v 2/r = ω 2r = (2π/t) 2R4. Centripetal force fcenter = mv 2/r = mω 2 * r = m (2π/t) 2 * r.

5. Period and frequency T= 1/f 6. The relationship between angular velocity and linear velocity v = ω r.

7. The relationship between angular velocity and rotational speed ω=2πn (frequency and rotational speed have the same meaning here).

8. Main physical quantities and units: arc length (s), meter (m), angle (φ), radian (rad), frequency (f) and Hz.

Period (t): second (s) speed (n): r/s radius (r): m (m) linear speed (v): m/s.

Angular velocity (ω): rad/s centripetal acceleration: m/s2.

Note: (1) The centripetal force can be provided by a specific force, resultant force or component force, and the direction is always perpendicular to the speed direction. (2) The centripetal force of an object in uniform circular motion is equal to the resultant force. The centripetal force only changes the direction of the speed, but does not change the size of the speed, so the kinetic energy of the object remains unchanged, but the momentum is constantly changing.

3) Gravity

1. Kepler's third law T2/R3 = k (= 4π 2/GM) R: orbital radius t: period k: constant (independent of planetary mass).

2. The law of gravitation F = GM1m2/R2G = 6.67×10-11nm2/kg2 is on their line.

3. Gravity and acceleration of gravity on celestial bodies GMM/r 2 = mg g = GM/r 2 r: celestial body radius (m)

4. Orbital velocity, angular velocity and period of the satellite V = (GM/R)1/2ω = (GM/R3)1/2t = 2π (R3/GM)1/2.

5. The first (second and third) cosmic velocity V 1=(g and r)1/2 = 7.9 km/SV2 =1.2 km/SV3 =16.7 km/s.

6. Geosynchronous satellite GMM/(r+h) 2 = m * 4π 2 (r+h)/T2H ≈ 3.6 km h: the height from the earth's surface.

Note: (1) The centripetal force required for celestial motion is provided by gravity, and f center =F million. (2) The mass density of celestial bodies can be estimated by applying the law of universal gravitation. (3) Geosynchronous satellites can only run over the equator, and the running period is the same as the earth rotation period. (4) When the orbit radius of the satellite decreases, the potential energy decreases, the kinetic energy increases, the speed increases and the period decreases. (5) The maximum circling speed and minimum launching speed of the Earth satellite are 7.9 km/s. ..

mechanical energy

work

(1) Two conditions for doing work: the force acting on an object.

The distance that an object passes in the direction of the tunnel.

(2) The magnitude of work: W=Fscosa Work is the unit of scalar work: Joule (J)

1J= 1N*m

When 0

When a= pie /2 w=0 (cos pie /2=0) F does not work.

Dangpai /2

(3) The solution of the overall work:

W total = w 1+w2+w3 ... well-nourished.

W total =F plus Scosa

2. Strength

(1) Definition: the ratio of the work to the time taken to complete it.

Power is the scalar unit of power: Watt (W)

This formula is the average power.

1w = 1J/s 1000 w = 1kw

(2) Another expression of power: P=Fvcosa

When f and v are in the same direction, P=Fv. (at this time, cos0 degree = 1).

This formula can be used to calculate the average power and instantaneous power.

1) average power: when v is the average speed,

2) instantaneous power: instantaneous speed when v is t.

(3) Rated power: refers to the maximum output power when the machine works normally.

Actual power: refers to the output power of the machine in actual work.

During normal operation: actual power ≤ rated power.

(4) Locomotive motion problem (premise: resistance F remains unchanged)

P=Fv F=ma+f (from Newton's second law)

There are two modes of car starting.

1) The car starts at constant power (A decreases until 0).

The p constant v is increasing and f is decreasing, especially f = ma+f.

When f decreases =f, v has a maximum value at this time.

2) The car moves at a constant acceleration (A starts to be constant and gradually decreases to 0).

A is constant, F is constant (F = MA+F), V is increasing, and P is gradually increasing to the maximum.

P at this time is rated power, that is, P must be.

The p constant v is increasing and f is decreasing, especially f = ma+f.

When f decreases =f, v has a maximum value at this time.

3. Work and energy

(1) Relationship between work and energy: The process of doing work is the process of energy conversion.

Work is a measure of energy conversion.

(2) The difference between work and energy: energy is a physical quantity determined by the motion state of an object, that is, a process quantity.

Work is a physical quantity related to the state change process of an object, that is, the state quantity.

This is the fundamental difference between work and energy.

4. kinetic energy. theorem of kinetic energy

(1) Definition of kinetic energy: the energy possessed by an object due to its motion. It is represented by Ek.

The expression ek = 1/2mv 2 can be a scalar or a process quantity.

Unit: joule (j)1kg * m 2/s 2 =1j.

(2) The content of kinetic energy theorem: the work done by external force is equal to the change of kinetic energy of an object.

The expression w = Δ ek =1/2mv2-1/2mv02.

Scope of application: constant force work, variable force work, segmented work and full work.

5. Gravity potential energy

(1) Definition: The energy that an object has because it is lifted. Use Ep to express.

The expression Ep=mgh is a scalar unit: joule (j)

(2) the relationship between gravitational work and gravitational potential energy

W weight =-δ EP

The change of gravitational potential energy is measured by gravity doing work.

(3) The characteristics of gravity work: it is only related to the initial and final position, and has nothing to do with the motion path of the object.

The potential energy of gravity is relative and related to the datum plane, generally taking the ground as the datum plane.

The change of gravitational potential energy is absolute and has nothing to do with the reference plane.

(4) Elastic potential energy: the energy possessed by an object due to deformation.

Elastic potential energy exists in an object with elastic deformation, which is related to the size of deformation.

The change of elastic potential energy is measured by elastic work.

6. Law of Conservation of Mechanical Energy

(1) mechanical energy: kinetic energy, gravitational potential energy and elastic potential energy.

Total mechanical energy: E=Ek+Ep is scalar and relative.

The change of mechanical energy is equal to work without gravity (such as work done by resistance)

Δ δE = W Non-weight

Mechanical energy can be transformed into each other.

(2) Law of Conservation of Mechanical Energy: The kinetic energy and gravitational potential energy of an object only when gravity does work.

Mutual transformation occurs, but the mechanical energy remains unchanged.

Expression: Ek 1+Ep 1=Ek2+Ep2. Only gravity works.

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Compilation table of physics formulas and laws in senior high school

First of all, mechanics

Hooke's law: F = kx (x is elongation or compression; K is the stiffness coefficient, which is only related to the original length, thickness and material of the spring)

Gravity: G = mg (g varies with the height, latitude and geological structure above the ground; Gravity is about equal to the gravity of the earth on the ground)

3. To find the resultant force of f, use the parallelogram rule.

Note: The synthesis and decomposition of (1) force follow the parallelogram law.

(2) the resultant force range of the two forces: F 1-F2 F 1+F2.

(3) The resultant force can be greater than, less than or equal to the component force.

4. Two equilibrium conditions:

* * * The equilibrium condition of an object under the action of point force: the resultant force of an object at rest or moving in a straight line at a constant speed is zero.

F =0 or: Fx =0 Fy =0.

Inference: [1] If three non-parallel forces act on an object and are balanced, then these three forces must be * * * points.

[2] Three * * * point forces act on an object, which is balanced, and the resultant force of any two forces is equal and opposite to the third force.

(2) The equilibrium condition of an object with a fixed rotating shaft: the algebraic sum of moments is zero.

Torque: M=FL (L is the arm of force and the vertical distance from the rotating shaft to the line of force)

5, the formula of friction:

(1) Sliding friction: f= FN

Description: ① FN is the elastic force between contact surfaces, which can be greater than g; It can also be equal to g; It can also be less than g.

② is the sliding friction coefficient, which is only related to the material and roughness of the contact surface, and has nothing to do with the size of the contact area, the relative motion speed of the contact surface and the positive pressure n. 。

(2) Static friction: Its magnitude is related to other forces, which is solved by the equilibrium condition of the object or Newton's second law, and is not proportional to the positive pressure.

Size range: O of static FM(FM is the maximum static friction, which is related to positive pressure)

Description:

Friction can be the same as or opposite to the direction of motion.

B, friction can do positive work, negative work or no work.

C the direction of friction is opposite to the direction of relative motion between objects or the direction of relative motion trend.

D, stationary objects will be affected by sliding friction, and moving objects will be affected by static friction.

6. Buoyancy: F= gV (attention unit)

7. Gravity: F=G

Applicable conditions: the gravitational force between two particles (or can be regarded as particles, such as two uniform spheres).

G is a gravitational constant, which was first measured by Cavendish with a torsion balance device.

Applications in celestial bodies: (m- celestial mass, m- satellite mass, r- celestial radius, g- gravitational acceleration of celestial surface, height from h- satellite to celestial surface)

First, gravity = centripetal force

G

B, near the surface of the earth, gravity = gravity.

Mg = gram = gram

First cosmic speed/speed [7.9 kilometers per second]

mg = m V=

8. coulomb force: F=K (applicable condition: force between two charges in vacuum)

Electric field force: f = eq (the direction of f and electric field strength can be the same or opposite).

10, magnetic field force:

Lorentz force: the force of a magnetic field on a moving charge.

Formula: f=qVB (BV) direction-left hand rule

Ampere force: the force of magnetic field on current.

Formula: F= BIL (two-way) left-handed rule

1 1, Newton's second law: f = ma or Fx = m ax Fy = m ay.

Scope of application: macro and low-speed objects

Understanding: (1) Vector (2) Instantaneity (3) Independence

Homogeneity homogeneity homogeneity homogeneity

12, uniform linear motion:

Basic law: Vt = V0+a t S = vo t +a t2.

Several important inferences:

(1) Vt2-V02 = 2as (uniformly accelerated linear motion: A is positive, uniformly decelerated linear motion: A is positive)

(2) Instantaneous velocity at the intermediate moment of section 2)ab:

Vt/2 = = (3) Instantaneous velocity of the displacement midpoint of AB section:

Vs/2 =

Uniform speed: vt/2 = vs/2; Uniform acceleration or uniform deceleration linear motion: uniform acceleration linear motion with initial velocity Vt/2 zero and displacement ratio within 1s, 2s, 3s ... ns is12: 22: 32 ... N2; 1s, the displacement ratio in 2s and 3s ... ns is1:3: 5 ... (2n-1); 1 meter time ratio, the second meter, the third meter ... the nth meter is 1: ...

No matter whether the initial velocity is zero or not, the displacement difference of a particle moving in a uniform linear motion in consecutive adjacent equal time intervals is constant: s = aT2 (a-acceleration t of uniform linear motion-time of each time interval).

Vertical throwing motion: the rising process is a uniform deceleration linear motion, and the falling process is a uniform acceleration linear motion. The whole process is a uniform deceleration linear motion with initial velocity VO and acceleration g.

Maximum lifting height: H =

(2) Rise time: t=

(3) When ascending and descending through the same position, the acceleration is the same, but the speed is equivalent to the opposite.

(4) The time of rising and falling through the same displacement is equal. Time from throwing to falling back: t =

(5) Formula applicable to the whole process: S = VOT-GT2VT = VO-GTT.

Vt2 -Vo2 =-2 gS (S, Vt's understanding of the positive and negative signs of s, Vt)

14, uniform circular motion formula

Linear speed: V= R =2f R=

Angular velocity: =

Centripetal acceleration: a =2 f2 R

Centripetal force: F= ma = m2 R= mm4n2 R.

Note: (1) The centripetal force of an object in uniform circular motion is the resultant force on the object and always points to the center of the circle.

(2) The centripetal force of satellites orbiting the earth and planets orbiting the sun is provided by gravity.

The centripetal force of the extranuclear electrons of hydrogen around the nucleus is provided by the coulomb force of the nucleus to the extranuclear electrons.

15, the formula of flat throwing motion: the combined motion of uniform linear motion and uniform acceleration linear motion, the initial velocity is zero.

Horizontal component motion: horizontal displacement: x= vo t Horizontal component velocity: vx = vo.

Vertical component motion: vertical displacement: y =g t2 vertical component velocity: vy= g t.

tg = Vy = Votg Vo =Vyctg

V = Vo = Vcos Vy = Vsin

If any two of the seven physical quantities Vo, Vy, V, X, Y and T are known, the other five physical quantities can be obtained according to the above formula.

16, momentum and impulse: momentum: P = mV impulse: I = F t

(attention vector)

17, momentum theorem: the impulse of the resultant force of external forces on an object is equal to the change of its momentum.

Formula: f and t = mv'-mv (stress analysis and positive direction are the key points in solving problems)

18, Law of Conservation of Momentum: The total momentum of an interacting object system remains unchanged if it is not subjected to external forces or the sum of external forces is zero. (Research object: two or more interactive objects)

Formula: m1v1+m2v2 = m1v1'+m2v2' or p 1 =- p2 or p1+p2 = o = o.

Applicable conditions:

(1) The system is not affected by external force. (2) The system is subjected to external force, but the resultant force is zero.

(3) When the system is subjected to external force, the resultant force is not zero, but it is far less than the interaction force between objects.

(4) The resultant force of the system in a certain direction is zero, and the momentum in that direction is conserved.

19, work: W = Fs cos (applicable to the calculation of constant force work)

Understand positive work, zero work and negative work

(2) Work is a measure of energy conversion.

Gravitational work. Measurement. Variation of gravitational potential energy.

Work done by electric field force-measurement-change of electric potential energy

Work-measurement of molecular force-change of molecular potential energy

Work done by external force-measurement-kinetic energy change.

20. kinetic energy and potential energy: kinetic energy: Ek =

Gravitational potential energy: Ep = mgh (related to the selection of zero potential energy surface)

2 1, kinetic energy theorem: the total work done by external force is equal to the change (increment) of kinetic energy of an object.

Formula: W = Ek = Ek2-Ek 1 = 22, law of conservation of mechanical energy: mechanical energy = kinetic energy+gravitational potential energy+elastic potential energy.

Condition: The system only has internal gravity or elasticity to do work.

Formula: mgh 1+ or Ep minus = Ek plus.

23. Conservation of energy (relationship between work and energy conversion): In a system with mutual friction, the reduced mechanical energy is equal to the work done by friction.

E = Q = f S phase

24. Power: p = (average power of internal force acting on an object in t time)

P = FV (F is traction, not resultant force; When v is instantaneous speed, p is instantaneous power; When v is the average speed, p is the average power; When p is constant, f is proportional to v)

25. Simple harmonic vibration: restoring force: F = -KX acceleration: a =-

Formula of period of simple pendulum: T= 2 (independent of pendulum mass and amplitude)

(Understanding) The periodic formula of the spring oscillator: T= 2 (related to the oscillator mass and spring stiffness coefficient, but not to the amplitude).

26. Relationship among wavelength, wave velocity and frequency: V == f (applicable to all waves)

Second, heat.

1, the first law of thermodynamics: U = Q+W

Symbolic law: when the outside world does act on an object, W is "+". When an object does external work, W is "-";

The object absorbs heat from the outside, and q is "+"; An object radiates heat to the outside world, and q is "-".

The internal energy increment u of an object is "+"; The internal energy of an object decreases and u is "-".

2, the second law of thermodynamics:

Expression 1: It is impossible to transfer heat from a low-temperature object to a high-temperature object without causing other changes.

Expression 2: It is impossible to absorb heat from a single heat source and use it all for external work without causing other changes.

Statement 3: The second perpetual motion machine is impossible to make.

3, the ideal gas state equation:

(1) Applicable conditions: For a certain quality of ideal gas, three state parameters change at the same time.

(2) Formula: Constant

4. Thermodynamic temperature: T = t+273 unit: K.

(Absolute zero is the limit of low temperature, which is impossible to reach)

Third, electromagnetism.

(1) DC circuit

1, the definition of current: I = (microscopic expression: I=nesv, n is the number of charges per unit volume)

2. Law of resistance: R=ρ (resistivity ρ is only related to the properties and temperature of the conductor material, and has nothing to do with the cross-sectional area and length of the conductor).

3. Series and parallel resistances:

Series connection: r = r 1+R2+R3+...+RN.

Parallel connection: two resistors are connected in parallel: R=

4. Ohm's law: (1) Ohm's law of some circuits: U=IR.

(2) Ohm's Law of Closed Circuit: I =

Terminal voltage: U = -I r= IR.

Power output: = Iε-Ir =

Power supply thermal power:

Power efficiency: = =

(3) Electricity and electricity:

Electric power: W=IUt electric heating: Q= electric power: P=IU.

For pure resistance circuit: W=IUt= P=IU =

For non-pure resistance circuit: w = iutpiu.

(4) Series connection of battery packs: the electromotive force of each battery is `internal resistance is'. When n batteries are connected in series:

Electromotive force: ε=n Internal resistance: r=n

(2) Electric field

1, properties of electric field force:

Electric field strength: (definition) E = (q is the probe charge, and the field strength has nothing to do with Q)

Electric field strength of point charge: E = (note field strength vector)

2, the nature of electric field energy:

Potential difference: U = (or W = U q)

UAB = φA - φB

The relationship between the work done by electric field force and the change of electric potential energy: U =-W

3. Relationship between field strength and potential difference in uniform electric field: E = (d is the distance along the field strength direction)

4, the motion of charged particles in the electric field:

Uranium? Uq =mv2

② deflection: motion decomposition: x = VO t；; vx = voy = a t2vy= a t

a =

(3) Magnetic field

Several typical magnetic fields: charged straight line, charged solenoid, annular current and geomagnetic field distribution.

The effect of magnetic field on live wire (Ampere force): F = BIL (B⊥I is required, and the direction of force is determined by the left-handed rule; If B‖I, the magnitude of the force is zero)

The effect of magnetic field on moving charge (Lorentz force): F = qvB (v⊥B is required, and the direction of force is also determined by the left-handed rule, but the four fingers must point in the direction of positive charge; If B‖v, the magnitude of the force is zero)

Charged particles move in a magnetic field: When charged particles are vertically injected into a uniform magnetic field, Lorentz force provides centripetal force, and charged particles move in a uniform circle. Namely: qvB =

Available: r =, T = (determining the center and radius is the key)

(4) Electromagnetic induction

1, direction determination of induced current: ① conductor cutting magnetic induction line: right-handed rule; ② Flux change: Lenz's law.

2. The magnitude of induced electromotive force: ① E = BLV (L is required to be perpendicular to B, V, otherwise it will be decomposed into vertical direction) ② E = (① Formula is often used to calculate instantaneous value, ② Formula is often used to calculate average value).

(5) alternating current

1, generation of alternating current: the coil rotates at a uniform speed in the magnetic field. If the coil rotates from the neutral surface (the plane of the coil is perpendicular to the direction of the magnetic field), the instantaneous value of the induced electromotive force is e = Em sinωt, and the maximum value of the induced electromotive force is Em = nBSω.

2. Effective value of sinusoidal alternating current: E =；; u =； I =

(Effective value is used to calculate the work done by current, heat generated by conductor, etc. ; The average value of alternating current is used to calculate the amount of charge passing through the conductor)

3. Influence of inductance and capacitance on alternating current:

Inductance: DC current, AC resistance; Pass the low frequency and block the high frequency.

Capacitance: AC on, DC off; Pass high frequency and block low frequency.

Resistance: AC and DC can pass, and there are obstacles.

4, transformer principle (ideal transformer):

① voltage: ② power: P 1 = P2.

③ Current: If there is only one secondary coil:

If there are multiple secondary coils: n 1I 1= n2I2+n3I3.

Period of electromagnetic oscillation (LC loop): T = 2π.

Fourth, optics.

1, law of refraction of light: n =

Refractive index of medium: n =

2. Conditions for total reflection: ① light is emitted from light dense medium into light sparse medium; ② The incident angle is greater than or equal to the critical angle. Critical angle C: sin C =

3, double seam interference law:

① distance difference δ s = (n = 0, 1, 2,3-) bright stripes

(2n+ 1) (n = 0, 1, 2,3-) dark stripes.

Distance between two adjacent bright stripes (or dark stripes): δδX =

4. Photon energy: E = hυ = h (where h is Planck constant, equal to 6.63× 10-34JS, υ is the frequency of light) (photon energy can also be written as E = m c2).

(Einstein) photoelectric effect equation: Ek = hυ-W (where Ek is the maximum initial kinetic energy of photoelectrons and w is the work function of metals, which is related to the types of metals).

5. wavelength of matter wave: = (where h is Planck constant and p is momentum of the object)

Verb (abbreviation for verb) atom and nucleus

Energy level structure of hydrogen atom.

When an atom transitions between two energy levels, it emits (or absorbs) photons:

hυ = E m - E n

Nuclear energy: energy released during nuclear reaction.

Equation of mass and energy: E = m C2 nuclear reaction releases nuclear energy: δ e = δ mc2.

Review recommendations:

1, the main knowledge of physics in senior high school is mechanics and electromagnetism, and the college entrance examination accounts for 38% each. These contents mainly appear in calculation questions and experimental questions.

The key points of mechanics are: ① the relationship between force and object motion; ② The application of the law of universal gravitation in astronomy; (3) the application of the law of conservation of momentum and energy; ④ Vibration and waves, etc. ⑤ ⑤

The first task of solving mechanical problems is to clarify the research object and process, analyze the physical situation and establish the correct model. There are three ways to solve the problem: ① If it is a process of uniform change, it can usually be solved by kinematics formula and Newton's law; ② If the problem of force and time is involved, it can usually be solved from the point of view of momentum, and the representative laws are momentum theorem and momentum conservation law; (3) If problems of force and displacement are involved, they can usually be solved from the point of view of energy, and the representative laws are kinetic energy theorem and mechanical energy conservation law (or energy conservation law). The latter two methods are especially suitable for variable acceleration motion with complex process, but it should be noted that both conservation laws are conditional.

The emphases of electromagnetism are: ① the essence of electric field; ② Circuit analysis, design and calculation; ③ Motion of charged particles in electric and magnetic fields; ④ Force problem, energy problem and so on in electromagnetic induction phenomenon.

2. Thermology, optics, atoms and nuclei each account for about 8% in the college entrance examination. Because the college entrance examination requires a wide range of knowledge, the scores of these contents are relatively small, so most of them appear in the form of selective examinations and experiments. However, we must not think that this part of the content is scored less and is not valued. Due to the lack of content and regularity, the score rate of this part should be high.