In order to find the recoil velocity of a spring

[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 into this problem? where am i going wrong?

 

[Astronuc]

One must use conservation of energy and momentum.

The Po-214 nucleus has a mass of 214 amu (1 amu ~ 1.66 x 10^-27 kg)

http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/nucuni.html#c1

or use the mass of the alpha as 4 amu and that of the Po-214 nucleus as 214 amu.