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Unit and uncertainty, Mechanics, Motion, Material, Pressure, Wave basis,…
Unit and uncertainty
SI base unit
The basic units of the International System of Units Length (m), mass (kg), time (s), current (A), thermodynamic temperature (K), amount of matter (mol), luminous intensity (cd)
Systemic error
Caused by instrument/method deviation, the calibration instrument can be corrected.
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Random error
Caused by accidental factors, multiple measurements can reduce the average.
Mechanics
Statics (Force Analysis)
Force equilibrium: \sum F = 0 (concurrent forces), \sum M = 0 (moment equilibrium)
Energy (Work and Energy)
Work: W = Fs\cos\theta; Conservation of mechanical energy: E_k + E_p = \text{constant} (only gravitational force does work)
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Motion
Motion Graphs (x-t, v-t)
Slope of x-t graph = velocity; Slope of v-t graph = acceleration, area under v-t graph = displacement
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Material
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Stress and Strain
Stress: \sigma = \frac{F}{A}; Strain: \varepsilon = \frac{\Delta L}{L}; Young’s modulus: E = \frac{\sigma}{\varepsilon}
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Wave basis
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Wave Physical Quantities
Wave speed: v = \lambda f = \frac{\lambda}{T} (\lambda = wavelength, f = frequency, T = period)
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Electromagnetic wave
Electromagnetic Spectrum
Radio waves → Microwaves → Infrared → Visible light → Ultraviolet → X-rays → Gamma rays (frequency increases, wavelength decreases)
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Stationary waves
Formation Conditions
Superposition of two coherent waves with the same frequency, amplitude and wave speed, propagating in opposite directions
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