# How does one develop a Hamiltonian for a free particle?

1. Jul 8, 2007

### ehrenfest

The equation for the Hamiltonian is H = T + V. Can someone explain how you can use this to get this equation for a free particle:

$$i\hbar|\psi'> = H|\psi> = P^2/(2m)|\psi>$$

The first part is obviously Schrodinger's equation but how do you get H = P^2/2m?

Go to page 151 at the site below if you do not understand this question.

Last edited: Jul 8, 2007
2. Jul 8, 2007

### christianjb

For a free particle V=0.

You're left with the KE operator.

Classically, KE=p^2 /2m.

QM, KE operator = p^2 / 2m, with p=-ihbar d/dx (in 1D)

3. Jul 9, 2007

### ehrenfest

I see. Thanks.