Here is an oscillating ball.
Its motion can be described as follows:
This information concentrates on what phase of the cycle is being
executed. It is not concerned with the particulars of amplitude.
First the ball is at v = 0 at the right
Then it moves with v < 0 through the centre to the left
Then it is at v = 0 at the left
Then it moves with v > 0 through the centre to the right
Then it repeats...
Mathematically, the phase is the "w t" in:
The ubiquitous ball undergoes oscillations of amplitude A. What is the
phase in the following situations?