In order to find the recoil velocity of a spring

1. Oct 14, 2007

jgibbon2

The nucleus of Po^214 decays radioactively by emitting an alpha particle (mass 6.65×10−27 kg) with kinetic energy 1.16×10−12 J, as measured in the laboratory reference frame.

a) Assuming that the Po was initially at rest in this frame, find the magnitude of the recoil velocity of the nucleus that remains after the decay.

in order to find the recoil velocity... i have tried v=-(sqrt KE*2m)/m .... is there a known mass for Polonium that you plug in to this problem? where am i going wrong?

2. Oct 15, 2007