When I learnt about operators, I learnt <x> = ∫ Ψ* x Ψ dx, <p> = ∫ Ψ* (ħ/i ∂/∂x) Ψ dx. The book then told me the kinetic energy operator(adsbygoogle = window.adsbygoogle || []).push({});

T = p^{2}/2m = -ħ^{2}/2m (∂^{2}/∂x^{2})

I am just think that why isn't it -ħ^{2}/2m (∂/∂x)^{2}

Put in other words, why isn't it the square of the derivative, but differentiating it twice?

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# I About operators

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