Rutherford scattering and momentum

[Kajan thana]

I read from a text that Rutherford found out that all the mass must be concentrated in the middle of the atom due to fast-moving alpa ( high momentum) is deflected back at 180 degrees.

I am wondering if there is going to be no contact collision due to the the kinetic energy being converted into potential energy then back to kinetic energy when it is returning back; why are we considering momentum in this concept?

 

[Replusz]

Momentum and kinetic energy are linked by a factor of 1/2v when considering non-relativisticity.
So if something has a large MOMENTUM, it has a large kinetic energy also.