# Speed of the electron after the collision

1. May 12, 2010

### Foshizzle387

An electron with a speed of 5.50×10^6 m/s, collides with an atom. The collision excites the atom from its ground state (0eV) to a state with an energy of 3.50eV

What is the speed of the electron after the collision?

Dont know where to start.

2. May 12, 2010

### rock.freak667

Well how much of the initial energy of the electron is transferred to the atom to cause the excitation?

3. May 12, 2010

### Lil_Aziz1

Conservation of Energy:

$$KE_e_i = KE_{e_{f}} + E_{atom}$$ assuming that the atom is initially at rest.