Physics
🔒 Log in to trackmedium importance~1 Q in Tier 127 formulas⚡ 12 shortcuts6 subtopics
Every formula in this topic, grouped by subtopic. Print it and pin it above your desk.
SI units, conversions and measuring instruments
Kilowatt-hour
1\ \text{kWh} = 3.6 \times 10^{6}\ \text{J}
1 'unit' of electricity
Horsepower
1\ \text{hp} \approx 746\ \text{W}
Light year
1\ \text{ly} \approx 9.46 \times 10^{15}\ \text{m}
a unit of distance
Motion, gravitation, work-energy, fluids and levers
First equation of motion
v = u + at
Second equation of motion
s = ut + \tfrac{1}{2}at^{2}
Third equation of motion
v^{2} = u^{2} + 2as
Newton's second law
F = ma = \frac{\Delta p}{\Delta t}
p = mv
Law of gravitation
F = \frac{G m_1 m_2}{r^{2}}
G = 6.67 × 10⁻¹¹ N m² kg⁻²
Kinetic and potential energy
KE = \tfrac{1}{2}mv^{2},\quad PE = mgh
Work and power
W = Fs\cos\theta,\quad P = \frac{W}{t}
1 W = 1 J/s
Pressure
P = \frac{F}{A},\quad P_{\text{liquid}} = h\rho g
unit pascal
Heat, temperature and sound
Temperature scales
\frac{C}{100} = \frac{F-32}{180} = \frac{K-273}{100}
−40 °C = −40 °F
Heat absorbed
Q = mc\,\Delta T
c = specific heat
Latent heat
Q = mL
no temperature change during phase change
Wave speed
v = f\lambda
speed = frequency × wavelength
Echo distance
d = \frac{v\,t}{2}
sound travels to the wall and back
Light — mirrors, lenses, eye, dispersion and scattering
Power of a lens
P = \frac{1}{f\,(\text{m})} = \frac{100}{f\,(\text{cm})}
unit dioptre
Lens formula
\frac{1}{f} = \frac{1}{v} - \frac{1}{u}
Cartesian sign convention
Mirror formula
\frac{1}{f} = \frac{1}{v} + \frac{1}{u}
f = R/2
Refractive index
n = \frac{c}{v}
c = 3 × 10⁸ m/s
Electricity, magnetism and the EM spectrum
Ohm's law
V = IR
Series resistance
R_s = R_1 + R_2 + \cdots
Parallel resistance
\frac{1}{R_p} = \frac{1}{R_1} + \frac{1}{R_2} + \cdots
two resistors: R₁R₂/(R₁+R₂)
Electric power
P = VI = I^{2}R = \frac{V^{2}}{R}
Joule heating
H = I^{2}Rt
Resistance of a wire
R = \rho\frac{L}{A}
ρ = resistivity
Nuclear physics, inventions and scientists
Mass–energy equivalence
E = mc^{2}
Einstein