It's better to be all inclusive

It's better to be all inclusive

A lot of formulas are summarized, but the key is that you can use them. First of all, you need to understand how the formulas come from and how to use them. You need to practice more. You can understand what the formulas are and where they should be used
Chapter one strength
Gravity: g = mg
friction:
(1) Sliding friction: F = μ FN, that is, the sliding friction is proportional to the pressure
(2) Static friction: 1. Newton's second law should be used in the calculation of general static friction
F = μ FN; ② there is a formula for calculating the maximum static friction force: F = μ FN (Note: the difference between μ here and μ in the sliding friction law, but in general, we think it is the same)
Composition and division of forces
(1) The composition and decomposition of forces should follow the parallelogram rule
(2) Specific calculation is to solve the triangle, and right triangle based
Chapter 2 linear motion
Velocity formula: VT = V0 + at ①
Displacement formula: S = v0t + AT2 ②
Velocity displacement relation: - = 2As ③
Average speed formula: = ④
= (v0 + vt) ⑤
= ⑥
The formula of displacement difference: △ s = AT2 ⑦
Formula explanation: (1) except for Formula 4, other formulas are only applicable to uniform speed change linear motion. (2) formula 6 refers to that in uniform speed change linear motion, the value of average speed in a certain period of time is exactly equal to the speed in the middle of this period of time, thus establishing a relationship between average speed and speed
6. For the uniformly accelerated linear motion with zero initial velocity, the following laws are established:
(1) At the end of 1t second, 2T second, 3T second The ratio of the velocity at the end of NT second is: 1: 2: 3 : n.
(2) . 1t seconds, 2T seconds, 3T seconds The ratio of displacement in NT seconds is: 12: 22: 32 : n2.
(3) In 1t second, 2T second, 3T second The displacement ratio in the nth second is: 1: 3: 5 : (2 n-1).
(4) In 1t second, 2T second, 3T second The ratio of the average speed in the nth second is: 1: 3: 5 : (2 n-1).
Chapter 3 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 at the same time
(3) Instantaneity: the previous formula reflects the instantaneous relationship between F and a
(4) Limitations: only set up in inertial frame, subject to macro low speed
2. Whole method and isolated method
The integral method does not need to consider the internal force of the whole (system). It is relatively simple to solve the problem with this method and is used for the calculation of acceleration and external force. The isolation method needs to consider the internal force, which is generally more complicated, but it must be used in the calculation of internal force. When choosing which object to isolate, we should select the one with less stress for isolation research
3. Overweight and weightlessness
When there is acceleration in the vertical direction, the phenomenon of overweight and weightlessness will occur. The essence of overweight and weightlessness is that the actual size of gravity does not match with the displayed size. It is not the change of the actual gravity, but the change of the displayed gravity
Chapter 4 balance of objects
1. Equilibrium condition: F = 0
2. The common methods to deal with the problem of object balance are as follows:
(1) When an object is only subjected to three forces, it is better to use the method of synthesis and decomposition. The method of synthesis is to transform the three forces on the object into two pairs of balanced forces through synthesis; the method of decomposition is to transform the three forces on the object into two pairs of balanced forces through decomposition
(2) When an object is subjected to more than four forces (including four forces), the method of orthogonal decomposition should be used. The method of orthogonal decomposition is to decompose first and then synthesize to transform it into two pairs of balanced forces
Chapter 5 uniform circular motion
1. Description of uniform circular motion
① The definition of linear velocity: v = (s refers to arc length or distance, not displacement
② The definition of angular velocity is as follows:=
③ The relationship between linear velocity and period: v=
④ The relationship between angular velocity and period is as follows
⑤ The 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) Centripetal force is the combined external force of uniform circular motion of an object. When calculating the centripetal force, the direction pointing to the center of the circle must be taken as the positive direction. The function of centripetal force is to change the direction of motion without changing the speed of motion. Centripetal force always does no work, so it cannot change the kinetic energy of the object, but it can change the momentum of the object
Chapter six gravitation
1. The universal gravitation exists between all things, from the stars in the universe to the micro molecules and atoms. But the universal gravitation between general objects is so small that we can not detect its existence. Therefore, we only need to consider the universal gravitation between objects and stars or between stars and stars
2. Law of gravitation: F = (that is, the magnitude of gravitation between two particles is directly proportional to the product of the masses of the two particles and inversely proportional to the square of the distance.)
Note: ① the law is only applicable to particles or uniform spheres; ② G is called the constant of gravitation, g = 6.67 × 10-11n? M2 / kg2
3. The relationship between gravity, centripetal force and universal gravitation
(1) Objects on the earth's surface: gravity and centripetal force are two components of universal gravitation (as shown in the figure, f shows universal gravitation, G shows gravity, and f shows centripetal force). The centripetal force here originates from the earth's rotation. However, because the angular velocity of the earth's rotation is very small, the centripetal force is very small compared with universal gravitation, so the following relationship holds:
F ≈ g > > F direction
Therefore, gravity acceleration and centripetal acceleration are two components of acceleration
A ≈ g > > a direction
Remember: gravity and gravitation are not the same thing on the surface of the earth
(2) An object that breaks away from the earth's surface and becomes a satellite: gravity, centripetal force and universal gravitation are the same thing, but they are different. That's why we write the following equation as soon as we talk about satellites
= m = m
4. The relationship between the linear velocity, angular velocity, period, centripetal acceleration and radius of the satellite
(1) . v = i.e. the larger the radius, the smaller the velocity. (2) = i.e. the larger the radius, the smaller the angular velocity
(3) T = 2, i.e. the larger the radius, the larger the period. (4). A = i.e. the larger the radius, the smaller the centripetal acceleration
Note: for V, t, a and R, as long as any one of them is determined, the other four quantities will be uniquely determined. The above quantitative conclusion does not require memory, but the qualitative conclusion must be remembered
Chapter 7 momentum
1. Impulse: I = ft, impulse is vector, direction is the same as the direction of force
2. Momentum: P = MV, momentum is also a vector, and its direction is the same as that of motion
3. Law of momentum: F = MVT – MV0
Chapter 8 mechanical energy
1. Work: (1) w = FS cos
(2) W = Pt (where "P" must be the average power)
(3) Wtotal = △ EK (Law of kinetic energy)
2. Power: (1) P = w / T
(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, the gravitational potential energy is also scalar, where "H" refers to the vertical distance from the center of gravity to the reference plane
5. Kinetic energy theorem: F = s = MV - MV
6. Law of conservation of mechanical energy: MV + MgH1 = MV + MgH2