Answer to Question #161805 in Physics for Jannatul Talha

Question

How initial phase is constant at periodic speeds?

Answer 1

Speeds are indeed periodic when we consider simple harmonic motion defined by sine or cosine functions:

$$v(t)=v_\text{max}\text{sin}{(\omega t+\phi_0),}$$

where $\phi_0$ is the initial phase. It is an argument and the function does not change its value, unlike $v(t)$.

However, initial phase is what determines how the motion begins and, thus, it is constant. The reason why the phase is called initial is because it plays role at the beginning of the motion.