Description of movement

1. The object model uses particles, ignoring shape and size; The revolution of the earth is a particle, and the rotation of the earth is great. The change of object position is accurately described by the ratio of displacement and velocity S to T, and the ratio of δ V to T is used for A. ..

2. It is a simple method to use the general formula method and the average velocity method, and the middle time velocity method, the initial velocity zero ratio method and the geometric image method are good methods to solve the motion. Take a free fall as an example, the initial velocity is zero, A is equal to G, the initial velocity is known vertically, the highest rise is known, the flight time is up and down, and the whole process slows down evenly. The speed at the central moment, the average speed is equal; The acceleration has a good square, and δ s is equal to the square of t.

3. Speed determines the motion of an object. In the direction of speed acceleration, the acceleration in the same direction decreases in the opposite direction, and the vertical corner does not rush forward.

Second, force.

1. Force analysis is the key to solve mechanical problems; Analyze the nature of the force and deal with it according to the effect.

2. Carefully analyze the stress and quantitatively calculate the seven forces; Whether to prompt gravity or not, and determine the elastic force according to the state; First there is elasticity, then there is friction, and relative motion is the foundation; Gravity exists, and the existence of electric field force is certain; Lorenz force and Ampere force are unified in essence; The forces perpendicular to each other are the greatest, and the forces parallel to each other are weak.

3. If the same row is oriented, the calculation result is only "quantity". If the direction of a quantity is uncertain, it means the calculation result; The resultant force of the two forces is small and large, and the two forces form a Q-angle clip, using the parallelogram method; The resultant force varies with q, only between the maximum value and the minimum value, and the multi-force resultant force closes the other side.

Multi-force problem can be solved by orthogonal decomposition, and trigonometric function can also be solved.

4. There are many methods for mechanical problems, and the whole is isolated and hypothetical; As a whole, we only need to look at the external force and solve the internal force isolation; Use the whole in the same state, otherwise isolation is much more used; Even if the state is different, the whole cow can do it; Assuming that a force exists or not, it is determined according to calculation; Limit method grasps the critical state, and procedural method does it in order; Orthogonal decomposition selects coordinates, and there are as many vectors on the axis as possible.

Third, Newton's law of motion.

1.f and other laws of horse and Newton produce acceleration because of force.

The resultant force is in the same direction as A, and the velocity variable is in the direction A. The smaller A is, the greater U is, as long as A and U are in the same direction.

2. The equivalent force of N and T is the apparent weight, and the product of mg is the actual weight; Overweight pays attention to visual weight, of which the constant is real weight; Acceleration is overweight and deceleration is overweight; Weight loss is determined by increase or decrease, and the total weight loss is zero.

Four, curve motion, gravity

1. The motion trajectory is a curve, the existence of centripetal force is a condition, the speed of curve motion changes, and the direction is the tangent to this point.

2. The centripetal force of circular motion, the relationship between supply and demand is in the heart, and the radial resultant force provides enough, which requires μ square ratio R and R, mrw square, and the balance between supply and demand is inseparable.

Gravity is born of mass and exists in all things in the world. It is because of the great mass of celestial bodies that gravity shows its magical power. Satellites orbit celestial bodies, and fast and slow satellites are determined by distance. The closer you get, the faster you get, and the farther you get, the slower you get. Synchronous satellites have a fixed speed, and the fixed point on the equator is empty.

V. Mechanical energy and energy

1. Determine the state to find kinetic energy, and analyze the process to find force and work. When the positive and negative work are added together, the kinetic energy increment is the same as it.

2. Make clear the two-state mechanical energy, and then look at the work done by the process force. The work outside "gravity" is zero, and the initial state and final state energy are the same.

3. Determine how much energy the state seeks, and then look at the process force of doing work. If you are active, you can change, and the initial and final energy are the same.

Six, electric field [elective 3- 1]

1. Coulomb's law of charge force, universal gravitation, like twin brothers, kQq and r square ratio.

2. There is an electric field around the charge, and F/Q defines the field strength. KQ is a point charge larger than r2, while U is a uniform electric field.

The electric field strength is a vector, and the positive charge is forced in the direction. Field lines are used to describe the electric field, and density indicates strength.

The nature of field energy is electric potential, which decreases along the field line. The work done by the field force is qU, and the theorem of kinetic energy cannot be forgotten.

4. There is an equipotential surface in the electric field, and draw an electric field line perpendicular to it. The direction is from high to low, and the area density is dense.

Seven, constant current [elective 3- 1]

1. When the charge moves directionally, the current is equal to q/t, the free charge is the internal cause and the voltage at both ends is the condition.

The normal load flows in a fixed direction and is measured by a series of ammeters. The external current of the power supply is negative, from negative to positive.

2. The law of resistance is based on three factors, that is, the temperature is constant, and the control variable is discussed. The resistance of r l is equal to that of S. ..

The current does work, the electric heating is the square of I, and so is the electric power, w versus t, and the voltage is multiplied by the current.

3. The basic circuits are connected in series and parallel, and the voltage division and shunt should be clear. Equivalent circuit is the key to complex circuit thinking.

4. Close part of the circuit, the external circuit and the internal circuit are ohms.

The voltage drop at the end of the road is equal to the electromotive force, but the total resistance current is.

Eight, magnetic field [elective 3- 1]

1. There is a magnetic field around the magnet, and the N pole is forced to orient; There is a magnetic field around the current, and the ampere determines the direction.

2.f ratio I l is the field strength, φ is equal to B S magnetic flux, and the magnetic flux density φ is equal to S, so the name of magnetic field strength is different.

3.BIL Ampere, pay attention to each other.

4. Lorentz force Ampere force, don't forget to throw it to the left.

Nine, electromagnetic induction [elective 3-2]

1. Electromagnetic induction generates electricity, and the change of magnetic flux is the condition. There is current when the loop is closed and power when the loop is open.

The magnitude of induced electromotive force and the rate of change of magnetic flux are known.

2. Lenz's law sets the direction and hinders the change. The conductor cuts the magnetic induction line, and the right-handed rule is more convenient.

3. Lenz's law is abstract, and it is reasonable to understand it from three aspects: hindering the increase or decrease of magnetic flux, resisting relative motion and trying to block self-induced current. Cold magnetism first looks at the original magnetic field, and the direction of the induced magnetic field depends on whether the magnetic flux increases or decreases, and Ampere will tell me the direction.

X. alternating current [elective 3-2]

1. The uniform magnetic field has a coil, which rotates to generate alternating current. The variation law of current and voltage electromotive force is chord line.

Neutral surface timing is sine and parallel plane timing is cosine.

2.NBSω is the maximum value, and the effective value is calculated by heat.

3. The transformer is used for AC, not constant current.

Ideal transformer, primary value, secondary value, equality is the principle.

The voltage ratio is proportional to the turns ratio; The current ratio is inversely proportional to the turns ratio.

Using the transformation ratio, if a certain number of turns is found, it can be converted into a turn ratio, which can be calculated conveniently.

Long-distance transmission, boost the voltage and reduce the current, otherwise the loss will be large and the user will step down.

Eleven, gaseous equation [elective 3-3]

Study the fixed mass of gas, determine the state and find the parameters. The absolute temperature is greater than t, and the volume is the volume.

Analysis of closure pressure, Newton's law helps you. The state parameters should be accurate, and the PV ratio t should be constant.

Twelve. Thermodynamic law

1. The first law of thermodynamics, the conservation of energy feels good. How much internal energy changes, etc. And you can't do less work with heat.

The positive and negative symbols should be accurate and understood by income and expenditure. Internal strength and heat absorption, internal energy increase is positive; External work and heat release, 2. The second law of thermodynamics, heat transfer is irreversible, work changes from heat to work, and direction is irreversible.

Thirteen, mechanical vibration [elective 3-4]

1. Simple harmonic vibration Remember that O is the starting point for calculating displacement, and the direction of restoring force always refers to the equilibrium position.

The size is proportional to the displacement, and the equilibrium position u is extremely large.

2.o-point symmetry Don't forget that vibration intensity is amplitude and vibration speed is period. One period is 4A, the period of a simple pendulum is l to g, and then the square root is multiplied by 2p. The period of the second pendulum is 2 seconds, and the pendulum length is about 1 m.

Simple pendulum reaches the center of mass, simple pendulum is isochronous.

3. The direction of vibration image is from bottom to top and from top to bottom; The vibration image depicts displacement, and the displacement of the top and bottom points is large, and the positive and negative sign direction refers to.

Fourteen, mechanical wave [elective 3-4]

1. Turn left on the left slope and right on the right slope. Peaks and valleys have no direction.

2. Follow the direction of transmission. If you want to climb from the valley to the top of the mountain, you have to push your feet down instead of moving up and down.

3. For images at different times, δ T is 1/4 or 3, and the particle motion is chaotic, so S and other VTs come in handy.

Fifteen, optics [elective 3-4]

1. Self-luminescence is a kind of light source, and the same kind of light propagates uniformly in a straight line. If you encounter obstacles, the propagation path should be changed.

There are two laws of reflection and refraction, and the law of refraction is the key. Optical media have refractive index, which is defined as sine ratio, or speed ratio, which is also caused by wavelength ratio.

2. Total reflection, remember that the incident light is dense. The incident angle is greater than the critical angle, and the refracted light is nowhere to be found.

Sixteen, physical optics

1. Light is electromagnetic wave, which will cause interference and diffraction. Diffraction has single slit and small hole, and interference has double slit and thin film. The middle of single slit diffraction is wider and the interference (fringe) spacing is similar. Small holes diffract light and interfere with dark rings and thin films, which have many uses. It can be used to measure workpieces and can also be made into antireflection films. Poisson's bright spot is diffraction, so we should master the interference formula. [Electives 3-4]

2. The illuminated metal can generate electricity, and the incident light is limited. The kinetic energy of photoelectrons is large or small, which is related to photon frequency. The number of photoelectrons is closely related to the intensity of light. The photoelectric effect can occur instantaneously, and the limit frequency depends on the work function. [Elective 3-5],

XVII. Momentum [Elective 3-5]

1. Determine the state to find momentum, analyze the process to find impulse, and determine the collinear direction. The calculation result is only "quantity". If the direction of a quantity is uncertain, the calculation result is displayed.

2. Determine the state to find momentum, and find impulse in the analysis process. If the external impulse is zero, the initial and final momentum are the same.