AS物理emm

物理period：time for one complete oscillation of a point in the wave frequency:number of oscillations per unit time of a point in a wave.

AS Physics

• Kinematics 运动学
  • Kinematics
    • average speed
      • distance traveled/ time
    • average velocity
      • displacement / time
    • instantaneous acceleration 瞬时速度
    • acceleration direction is same as the direction of the change in velocity
  • Acceleration motion
    • a= Δv/Δt
      • units：m/s^2
    • acceleration=gradient of velocity-time graph
    • velocity = gradient of a displacement–time graph
    • displacement =area under velocity-time graph
    • Equations
      • v=u+at
      • s=(u+v)t/2
      • s=ut+1/2at^2
      • v^2=u^2+2as
    • Free fall
      • Move under the influence of gravity only, regardless of its initial motion
      • g=9.80m/s^2 acceleration due to the gravity (direction: vertically downward)
• Dynamics 力学
  • Dynamics
  • Forces
  • Work energy and power
  • Momentum
• Matter and materials
• Electricity 电学
  • Electric current
  • Kirchhoff‘s laws
  • Resistance and resistivity
  • Practical circuits
• Waves 波
  • Waves
    • Progressive wave
      • period：time for one complete oscillation of a point in the wave frequency:number of oscillations per unit time of a point in a wave.
        • f=1/T
      • intensity = power/area intensity ∝ (amplitude)2 for a progressive wave
      • speed of wave：v= fλ
    • Transverse and longitudinal waves
      • Longitudinal wave
      • Transverse wave
      • Phase and phase difference 相位差
        • φ=x/λ✖️360 °
          • φ：phase difference between these particles in degrees
          • x：separation between two oscillating particles on a wave（两点之间在波上相隔的长度）
          • λ：wavelength
        • 当AB两点在同一水平直线上，φ=0° or 360° so they are in phase
    • Doppler effect for sound waves
    • Electromagnetic spectrum
      • All electromagnetic waves travel at the same speed of 3.0 × 108 m s−1 in a vacuum, but have different wavelengths and frequencies.
      • Electromagnetic waves are transverse waves.
      • increasing wavelength: γ-rays, X-rays, ultraviolet, visible, infrared, microwaves and radio waves.
    • Polarisation
      • 只有transverse wave可以发生偏振
      • I=I。cos^2θ
        • I。：intensity of incident入射 I：最终强度
  • superposition of waves
    • superposition
      • principle of superposition: when two or more waves meet at a point, the resultant displacement is the sum of the displacements of the individual waves
    • Diffraction
      • the spreading of a wave when it passes through a gap or past the edge of an object
    • Interference
      • 相位差180—两个波抵消；360—两个波相加
      • λ = ax / D
        • double slit
    • Diffraction grating
      • d sin θ = nλ 衍射
  • stationary waves
• Atomic structures
• Practical skills
  • SI Units
    • mass（kg）length（m）time（s）current（A）temperature（K）
    • prefixes
      • pico (p -12) nano (n -9) micro (μ -6) milli (m -3) centi (c -2) deci (d -1) kilo (k 3) mega (M 6) giga (G 9) tera (T 12)
  • precision&accuracy
    • precise
      • precise and accurate
    • accurate
  • Errors
    • systematic error
      • zero error
      • parallax
    • random error
      • can be reduced by making multiple
  • Uncertainty
    • calculate uncertainty
      • smallest division on the instrument used 测量仪器的最小分度
      • half the range of a number of readings of the measurements 一组数据的差值的一半
        • （数据的平均值±uncertainty）单位 平均值与uncertainty 精确到uncertainty的位数
    • percentage of uncertainty
      • uncertainty/measured value✖️100%➡️repeat to reduce
        • quantities➕➖
          • add absolute uncertainties
        • quantities✖️➗
          • add percentage uncertainties
  • scalar and vector
    • vector：magnitude+direction
    • scalar：only magnitude