In a pure sine wave, the maximum amplitude of particle velocity and the instantaneous pressure occur at different phases of the wave.
For a particle in a pure sine wave motion, the particle velocity is maximum when the displacement of the particle from its equilibrium position is zero. At this point, the particle is moving at its fastest, either in the positive or negative direction, depending on the phase of the wave.
On the other hand, the instantaneous pressure reaches its maximum when the displacement of the wave is maximum. This occurs when the particle is at its maximum displacement from the equilibrium position, either in the positive or negative direction.
To summarize:
- The maximum amplitude of particle velocity occurs when the displacement is zero.
- The maximum amplitude of instantaneous pressure occurs when the displacement is at its maximum.
It's important to note that the phase relationships and specific values depend on the mathematical equation describing the sine wave and the specific point in time being considered.