Let A be the displacement amplitude and ω be the angular frequency of S.H.M., Then,
Maximum velocity, v0 = ωA; ω = v0/A
Maximum acceleration,
\(a_0 = \omega^2\ A = (\frac{v_0}{A})^2\ A = \frac{v_0^2}{A}\)
∴ Displacement amplitude, A = \(\frac{v_0^2}{a_0}\)