\(x = A \sin (\omega t +\phi)\) \(....(1)\)

\(\frac{ dx }{ dt }= A \omega \cos (\omega t +\phi)\)

acceleration \((a)=\frac{d^{2} x}{d t^{2}}\)

\(a=-\omega^{2} A \sin (\omega t+\phi)\)

\(a =\omega^{2} A \sin (\omega t +\phi+\pi)\)\(.....(2)\)

from \((1) \;and\;(2),\) phase difference between displacement and acceleration is \(\pi .\)