A sinusoidal mechanical wave travelling along the +x–direction is represented by
y(x,t)=Asin(kx−ωt+ϕ).
Answer the following questions about the motion of the medium:
(i) Explain the physical difference between the velocity of an individual particle of the medium and the velocity of the wave itself.
(ii) Using the form of the given equation, justify qualitatively why the instantaneous speed of a particle can, at different instants, be greater than, equal to, or less than the speed with which the disturbance propagates.
(iii) For a fixed position x, identify two distinct phase values (kx−ωt+ϕ) for which the particle is momentarily at rest even though the wave keeps propagating. Give reasons for your answer.