Holding the spring constant fixed makes the total energy scale with amplitude squared. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

Two-metre amplitude stores four joules

With spring constant 2 newtons per metre and center position, amplitude 2 m gives total energy 4 J.

E=12kA2=12×2×22=4E={1\over 2}kA^{2}={1\over 2}\times2\times2^{2}=4
Amplitude-squared energy rowTotal, spring, and kinetic energies are checked.k=2 N/mA=2 mx=0 mE=4 JU=0 JK=4 J

Doubling amplitude makes four times the energy

With spring constant 2 newtons per metre and center position, amplitude 4 m gives total energy 16 J.

E=12kA2=12×2×42=16E={1\over 2}kA^{2}={1\over 2}\times2\times4^{2}=16
Amplitude-squared energy rowTotal, spring, and kinetic energies are checked.k=2 N/mA=4 mx=0 mE=16 JU=0 JK=16 J

Three times the amplitude makes nine times the energy

With spring constant 2 newtons per metre and center position, amplitude 6 m gives total energy 36 J.

E=12kA2=12×2×62=36E={1\over 2}kA^{2}={1\over 2}\times2\times6^{2}=36
Amplitude-squared energy rowTotal, spring, and kinetic energies are checked.k=2 N/mA=6 mx=0 mE=36 JU=0 JK=36 J