The amplitude \( A \) of a simple harmonic oscillator can be found using the total mechanical energy of the system. The total energy \( E \) is the sum of potential and kinetic energy:
\[
E = \frac{1}{2} k A^2.
\]
Solving for \( A \), we get:
\[
A = \sqrt{\frac{2E}{k}}.
\]
Thus, the amplitude \( A \) is related to the total energy \( E \) and the spring constant \( k \).