1) moving in a straight line at a uniform speed

1. average speed Vping =S/t (definition) 2. Useful inference Vt 2 -V0 2=2as.

3. Intermediate speed Vt/2= V level =(V t+V o)/2.

4. Final speed V=Vo+at

5. Intermediate position speed Vs/2=[(V_o2+V_t2)/2] 1/2.

6. Displacement S= V level T = V ot+AT2/2 = V t/2 t.

7. The acceleration A =(V _ T-V_o)/twit takes V_o as the positive direction, and A and V _ O are in the same direction (accelerating) a>0; On the other hand, a < 0

8. It is inferred experimentally that δS = aT2δS is the displacement difference in adjacent consecutive equal time (t).

9. Main physical quantities and units: initial velocity (V_o):m/ s acceleration (a):m/ s2 terminal velocity (VT): m/s.

Time (t): second displacement (s): meter 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=(V_t-V_o)/ t is only a measure, not a determinant. (4) Other related contents: particle/displacement and distance /S-T diagram /V-T diagram/velocity and rate/

2) Free fall

1. initial velocity V_o =0 2. Final speed V _ T = g T

3. Falling height h=gt2/2 (calculated from V_o position downwards)

4. Inference V t2 = 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≈ 10m/s2。 The gravity acceleration near the equator is small, the gravity acceleration at the high mountain is smaller than that at the flat ground, and the gravity acceleration is vertical downward.

3) Throw vertically upwards

1. displacement s = v _ ot–gt 2/22. The final speed v _ t = v _ o–g t (g = 9.8 ≈10m /S2).

3. It is useful to infer that V_t 2-V_o 2 =-2 g S 4. Maximum rising height H_max=V_o 2/(2g) (from the throwing point).

5. Round trip time t=2V_o/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 ascending and descending processes are symmetrical,

For example, at the same point, the speed is equal and the direction is opposite.

Second, the force (ordinary force, torque, force synthesis and decomposition)

1) ordinary force

1. gravity G=mg direction vertical downward g=9.8 m/s2 ≈ 10 m/s2 action point is suitable for the center of gravity near the earth's surface.

2. Hooke's Law F=kX direction along the recovery deformation direction K: stiffness coefficient (N/m) X: deformation variable (M)

3. Sliding friction force f=μN is opposite to the relative motion direction of the object μ: friction coefficient n: positive pressure (n)

4. Static friction force 0≤f Static ≤fm is opposite to the relative motion trend of the object, and fm is the maximum static friction force.

5. Gravity direction f = g m _1m _ 2/R2g = 6.67×10-1nm2/kg2 is on their connecting line.

6. The electrostatic force F = kq _1q _ 2/R2k = 9.0×109N m2/C2 is on their connecting line.

7. electric field force F=Eq E: field strength N/C q: electric field force exerted on positive charge by electric quantity c is in the same direction as field strength.

8. Ampere force f = b, l, sin, θ θ is the included angle between b and l when L⊥B: f = b, when B//L: F=0.

9. Lorentz force f=q V B sinθ θ is the angle between b and v when V⊥B: f=q V B, V//B: f=0.

Note: (1) The stiffness coefficient k is determined by the spring itself; (2) The friction coefficient μ has nothing to do with the pressure and contact area, but is determined by the material characteristics and surface conditions of the contact surface. (3) fm slightly larger than μN is generally considered as the symbol and unit of fm≈μN (4).

B: magnetic induction intensity (t), L: effective length (m), I: current intensity (a), V: charged particle velocity (m/S), Q: charged particle (charged body) electric quantity (c), (5) Ampere force and Lorentz force directions are determined by the left-hand rule.

2) Moment

1. Moment M=FL L is the arm of the corresponding force, which refers to the vertical distance from the line of action of the force to the rotating shaft (point).

2. Rotation balance condition M clockwise = M counterclockwise M unit is