← Mechanical Systems
1 Reading the notation
Physics uses Greek letters as standard variable names. Each is just a label, but you have to know which quantity it labels.📖 Symbols used in mechanics
10 termsCover the right column and check you can say what each one means.
- ω (omega)
- Angular velocity: how fast something rotates, in radians per second. ω = 2π/T = 2πf. Not to be confused with w for weight. Angular quantities use Greek letters; linear ones use Roman.
- θ (theta)
- Angular displacement, an angle, in radians.
- α (alpha)
- Angular acceleration, the rate of change of ω, in rad s⁻².
- τ (tau)
- Torque, the rotational equivalent of force. τ = Fr = Iα.
- I (capital I)
- Rotational inertia (moment of inertia): resistance to angular acceleration. Depends on mass AND how far that mass sits from the axis. In electricity the same letter means current. Context tells you which.
- L
- Angular momentum, L = Iω. Conserved when there is no external torque.
- T (period)
- The time for one complete cycle, in seconds. T = 1/f. Also used for tension and for temperature elsewhere: read the context.
- f (frequency)
- Cycles per second, in hertz (Hz). f = 1/T.
- A (amplitude)
- The maximum displacement from equilibrium in an oscillation.
- rad s⁻¹
- Radians per second. The ⁻¹ means “per”, so this is “radians per second”.