Explanation:
Potential energy, \(P E=\dfrac{1}{2} m \omega^{2} x^{2}\)
\(A\) is amplitude, \({(PE)_{\max }} = \frac{1}{2}m{\omega ^2}{A^2}\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\left( 1 \right)\)
Kinetic energy, \(K E=\dfrac{1}{2} m \omega^{2}\left(A^{2}-x^{2}\right)\)
At \(x=\dfrac{A}{2}, K E=\dfrac{1}{2} m \omega^{2}\left(A^{2}-\dfrac{A^{2}}{4}\right)\)
\(K E=\dfrac{3}{4} \times \dfrac{1}{2} m \omega^{2} A^{2}\)
\(K E=\dfrac{3}{4} P E_{\max }\)
(Given \(P E=25 J\))
\(K E=\dfrac{3}{4} \times 25=18.75 J\)