Khan Academy

Sound Properties: Amplitude, period, frequency, wavelength (K-A)

Speed of Sound (K-A)

Ultrasound medical imaging (K-A)

Why do sounds get softer? (K-A)

Doppler effect for a moving observer (K-A)

Doppler effect formula for observed frequency (K-A)

Doppler effect formula when source is moving away (K-A)

Doppler effect introduction (K-A)

Doppler effect: reflection off a moving object (K-A)

Beat frequency (K-A)

Constructive and Destructive interference-video (K-A)

When the source and the wave move at the same velocity (K-A)

Derivation of beat frequency formula (K-A)

Standing waves in closed tubes (K-A)

Standing waves in open tubes (K-A)

Standing waves on strings (K-A)

Wave interference-video (K-A)

Angled forces review (K-A)

Breaking down forces for free body diagrams (K-A)

Free body diagram with angled forces: worked example (K-A)

Friction review (K-A)

Intuition on static and kinetic friction comparisons (K-A)

Static and kinetic friction example (K-A)

Ice accelerating down an incline (K-A)

Inclined plane force components (K-A)