Chapter I Power
1. Gravity: G = mg
2. Friction:
(1) sliding friction: f = μFN, that is, sliding friction is proportional to pressure.
(2) Static friction: ① Newton's second law should be used in the calculation of general static friction, so remember not to use it indiscriminately.
f =μFN； ② There is a formula for calculating the maximum static friction force: f = μFN (note: μ here is different from μ in the sliding friction law, but in general, we think it is the same).
3. Composition and decomposition of force:
The combination and decomposition of (1) forces should follow the parallelogram law.
(2) The concrete calculation is to solve triangles, mainly right triangles.
Chapter II Linear Motion
1. Speed formula: vt = v 0+ in ①.
2. Displacement formula: s = v0t+at2 ②
3. Velocity-displacement relationship: -= 2as ③
4. Average speed formula: = ④
= (v0 + vt) ⑤
= ⑥
5. Displacement difference formula: △s = aT2 ⑦
Explanation of formula: (1) Except formula ④, the above formula is only applicable to linear motion with uniform change. (2) Formula ⑥ means that the average speed in a certain period is exactly equal to the speed in the middle of this period, thus establishing the relationship between the average speed and the speed.
6. For uniformly accelerated linear motion with zero initial velocity, the following laws hold:
(1). 1). 1 second, 2 seconds, 3 seconds ...........................................................................................................................................................
(2) The displacement time ... nt ratio. 1t second, 2T second, 3T second ... nt second is: 12: 22: 32:...:N2.
(3). 1T seconds, 2T seconds, 3T seconds ... and nt seconds are: 1: 3: 5:...:(2n- 1).
(4) 1T second, 2T second, 3T second, and nT second is: 1: 3: 5:...:(2n- 1).
Chapter III Newton's Law of Motion
1. Newton's second law: f = ma
Note: (1) Identity: The three quantities in the formula must belong to the same object.
(2) simultaneity: F and A must be simultaneous.
(3) Instantaneity: The previous formula reflects the instantaneous relationship between F and A. 。
(4) Limitation: It only holds in inertial system and is subject to macro low speed.
2. Integral method and isolation method:
The integral method does not need to consider the internal force in the whole system, so it is relatively simple to solve the problem and is used to calculate the acceleration and external force. The isolation method needs to consider the internal force, which is generally cumbersome, but it must be used when calculating the internal force. When choosing which object to isolate, choose the one with less stress for isolation research.
3. Overweight and weightlessness:
When there is acceleration in the vertical direction, overweight and weightlessness will occur. The essence of overweight and weightlessness is that the actual gravity does not match the displayed gravity, not that the actual gravity has changed, but that the displayed gravity has changed.
Chapter IV Object Balance
1. Equilibrium condition of an object: f = 0.
2. The common methods to deal with the problem of object balance are:
(1). When an object is only subjected to three forces, it is best to use the method of synthetic decomposition. The method of synthesis is to transform three forces on an object into two balanced forces through synthesis. The method of decomposition is to decompose three forces on an object into two pairs of balanced forces.
(2) When an object is subjected to more than four forces (including four forces), the orthogonal decomposition method should be adopted. Orthogonal decomposition method is the idea of decomposition first and then synthesis, which is transformed into two pairs of balance forces to deal with.
Chapter V Uniform Circular Motion
1. Description of uniform circular motion:
① Definition of linear velocity: v = (s refers to arc length or distance, not displacement.
②. Definition of angular velocity: =
③. Relationship between linear velocity and period: v =
④ Relationship between angular velocity and period:
⑤. Relationship between linear velocity and angular velocity: v = r
⑥. centripetal acceleration: a = or a =
2.( 1) centripetal force formula: f = ma = m = m
(2) The centripetal force is the resultant force of the uniform circular motion of an object, and the direction pointing to the center of the circle must be taken as the positive direction when calculating the centripetal force. The function of centripetal force is to change the direction of motion without changing the speed of motion. The centripetal force always does no work, so it can't change the kinetic energy of the object, but it can change the momentum of the object.
Chapter VI Gravity
1. Gravity exists in everything, from stars in the universe to microscopic molecules and atoms. But the gravity between ordinary objects is so small that we can't detect its existence. So we only need to consider the gravity between objects and stars or between stars and stars.
2. Law of universal gravitation: F = (that is, the magnitude of universal gravitation between two particles is directly proportional to the product of the masses of these two particles and inversely proportional to the square of the distance. )
Description: ① This law only applies to particles or uniform spheres; ② G is called the gravitational constant, and g = 6.67×10-11n? m2/kg2。
3. The relationship between gravity, centripetal force and gravity:
(1). Objects on the earth's surface: gravity and centripetal force are two components of universal gravitation (as shown in the figure, f stands for universal gravitation, g stands for gravity and f stands for centripetal force). The centripetal force here comes from the rotation of the earth. However, because the angular velocity of the earth's rotation is small and the centripetal force is less than gravity, the following relationship holds:
f≈G & gt； & gtf direction
Therefore, gravity acceleration and centripetal acceleration are two components of acceleration, and:
a≈g & gt； & gt One direction
Remember: gravity and gravity are not the same thing for objects on the earth's surface.
(2) Objects that leave the earth's surface and become satellites: gravity, centripetal force and gravitation are the same thing, but they are different statements. That's why when we talk about satellites, we immediately write the following equation:
= m = m
4. Relationship between linear velocity, angular velocity, period, centripetal acceleration and satellite radius:
(1).v= that is, the larger the radius, the smaller the speed.
(2).= That is, the larger the radius, the smaller the angular velocity.
(3).T =2, that is, the larger the radius, the larger the period.
(4).a= that is, the larger the radius, the smaller the centripetal acceleration.
Note: For the five quantities V, T, A and R, as long as any one of them is determined, the other four quantities are unique. The above quantitative conclusions do not need to be memorized, but the qualitative conclusions must be memorized.
Chapter VII Momentum
1. Impulse: I = Ft Impulse is a vector with the same direction as the acting force.
2. Momentum: p = mv Momentum is also a vector, and the direction is the same as the direction of motion.
3. Law of Momentum: F = MVT-MV0
Chapter VIII Mechanical Energy
1. Work: (1) W = Fs cos (only used when the force is constant and the object moves in a straight line).
(2) W = Pt ("P" here must be the average power)
(3) Total amount of W = △Ek (kinetic energy law)
2. Power: (1) p = W/t (can only be used to calculate the average power)
(2) p = Fv (both average power and instantaneous power can be calculated)
3. Kinetic energy: Ek = mv2 Kinetic energy is scalar.
4. Gravitational potential energy: Ep = mgh Gravitational potential energy is also a scalar, where "h" refers to the vertical distance from the center of gravity of the object to the reference plane.
5. Kinetic energy theorem: F equals s = mv-mv.
6. Law of conservation of mechanical energy: mv+mgh 1 = mv+mgh2.
All formulas of physics in senior one (2)
1, spring force: F = Kx (x is elongation or compression, and k is stiffness coefficient)
2. Friction formula: (1) Sliding friction:
Note: a and FN are elastic forces between contact surfaces, which can be greater than g; It can also be equal to g; It can also be less than g.
B, for sliding friction coefficient, only related to the contact surface material and roughness, and the contact surface.
The product size and the relative motion speed of the contact surface have nothing to do with the positive pressure FN.
(2) Static friction: It is solved by the equilibrium condition of the object or Newton's second law, and has nothing to do with the positive pressure.
Size range: o
Description: A. Friction can be the same as the direction of motion, or it can be opposite to the direction of motion, or it can form a certain angle with 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 also be affected by static friction.
3. Formula for finding the resultant force of F and F: (it is the included angle between F 1 and F2)
Note: The composition 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 uniform speed is zero.
F=o or FX = ofy = o.
5. Gravity:
A, gravity = centripetal force (celestial bodies, satellites, spacecraft do uniform circular motion around the earth)
G
、
B, near the surface of the earth, gravity = universal gravitation mg = g g = g
6. The first cosmic velocity G = m V=
Description: application in celestial bodies: m celestial body mass r celestial body radius g celestial body surface gravity acceleration
7. Kepler's third law: (generally used to solve the problem of celestial bodies orbiting the sun, it is more convenient)
8. Newton's second law: f = ma or Fx = m ax Fy = m ay.
Understanding: (1) Vector (2) Instantaneity (3) Independence (4) Identity
9, uniform linear motion:
Basic law: Vt = V0+a t S = vo t+a t2.
Several important inferences: (1) VT2-V02 = 2as (uniform acceleration linear motion: A is positive uniform deceleration linear motion: A is positive)
(2) Instantaneous speed at the intermediate moment: vt/2 = = =
(3) the instantaneous velocity of the displacement midpoint; Vs/2 =
Uniform speed: vt/2 = vs/2; Uniform acceleration or uniform deceleration linear motion: vt/2
(4) uniformly accelerated linear motion with zero initial velocity, at 1s, 2s, 3s? The displacement ratio within ……ns is12: 22: 32 ... N2;
1s, the displacement ratio in 2s and 3s ... ns is1:3: 5 ... (2n-1);
1 meter, the second meter, the third meter ... and the nth meter is 1: (... (
(5) Whether the initial velocity is zero or not, the position of a particle moving in a straight line at a uniform speed changes in consecutive adjacent equal time intervals.
The difference between displacements is a constant: s = aT2(a- acceleration t of uniform linear motion-time of each time interval).
10, vertical throwing motion: the ascending process is a uniform deceleration linear motion, and the descending process is a uniform acceleration linear motion. Overall process
It is a uniform deceleration linear motion with initial velocity of VO and acceleration of-g.
(1) Maximum rising height: H = (2) Rising 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. (5) Time from throwing to falling back to the original position: t =
(6) Formula applicable to the whole process: S = VO T-G T2VT = VO-G T.
Vt2-Vo2 = 2gs (understanding the sign of S and Vt)
1 1, uniform circular motion formula
Linear velocity: V= R =R2 f = angular velocity: =
Centripetal acceleration: a = 2 f2 R centripetal force: f = ma = m2r = m.
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 the uniform circular motion of the satellite around the earth and the planet around the sun is provided by gravity.
(3) The centripetal force of the electrons outside the hydrogen nucleus moving in a uniform circle around the nucleus is provided by the coulomb force of the nucleus to the electrons outside the nucleus.
(4) The centripetal force of particles moving in a uniform magnetic field is provided by Lorentz force.
,
12. Flat throwing motion: a combination of horizontal uniform linear motion and vertical free falling motion.
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
Time is determined by y= and t= (determined by falling height y)
Charged particles move in a uniform electric field, and u, d, l, m, q, v0 are known.
The combination of uniform linear motion in v0 direction and uniformly accelerated linear motion with zero initial velocity perpendicular to v0 direction.
(1) lateral movement:
(2) Deflection angle:
Note that the reverse extension of the terminal speed when passing is explained.
The intersection of this line and the initial velocity extension line is just at the midpoint of the horizontal displacement. This is the same as the conclusion of flat throwing motion.
(3) the kinetic energy increment in the process of crossing the electric field: EK = Eqy (note that Ey is generally not equal to qU acceleration).
(4) If it is accelerated by U 1 (initial velocity is zero), then
It can be seen that the lateral displacement y and deflection angle have nothing to do with the mass m and charge q of particles.
13, momentum and impulse: momentum: P = mV impulse: I = F t
14, momentum theorem: the impulse of the resultant force of external forces on an object is equal to the change of its momentum.
Formula: f = t = mv '-mv (stress analysis and positive direction are the key points in solving problems)
15, Law of Conservation of Momentum: If the interacting object system is not subjected to external force or the sum of external forces is zero,
Their total momentum remains unchanged. (research object: two or more interacting objects)
Formula: m1v1+m2v2 = m1v1'+m2v2' or p 1 = a p2 or p1+p2 = 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.
16, work: W = Fs cos (applicable to the calculation of constant force work)
(1) Understanding positive work, negative work and negative work
(2) Work is a measure of energy conversion.
Gravitational work-measurement-change 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.
(3) () (electron volt) is also a unit of energy.
(4) (only applicable to uniform electric field, where d is the distance between two points in the direction of electric field)
(5) (Definition formula), (Determination formula of dielectric constant determined by insulating medium)
17, kinetic energy and potential energy: kinetic energy: Ek = gravitational potential energy: Ep = mgh (related to the selection of zero potential energy surface)
18, kinetic energy theorem: the total work done by external force on an object is equal to the change (increment) of the kinetic energy of the object.
Formula: w = Ek = Ek2-Ek 1 = 19, 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.
20. Power: p = (average power of internal force acting on the 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)
2 1, simple harmonic vibration: restoring force: F = 1 KX acceleration: a =.
Simple harmonic motion period formula of a simple pendulum: T= 2 (independent of the mass and amplitude of the pendulum).
(g) Local acceleration of gravity as a function of altitude and latitude; North and South Pole G is the largest)
22. Relationship among wavelength, wave velocity and frequency: V= f = (applicable to all waves)