Vibrations and waves
Terms, formulas, and an interactive lab: a thread pendulum and a spring pendulum with sliders for the length, the mass, the stiffness and the amplitude, an animation of the swinging body and the graph x(t); a travelling wave with sliders for the frequency and the speed that give the wavelength and the graph y(x); an echo from a barrier in air, water and steel that gives the distance by the time of the sound's return.
Mechanical oscillations
Oscillatory motion, amplitude, period and frequency, free and forced oscillations, thread and spring pendulums, resonance.
Mechanical waves
A wave, transverse and longitudinal waves, wavelength and wave speed, the relations $\lambda = vT$ and $v = \lambda\nu$.
Sound. Echo
Sound as a mechanical wave, pitch and loudness, the speed of sound in different media, echo and finding the distance to a barrier.