Magnitude of the recoil velocity of the nucleus

[ledhead86]

The nucleus of 214Po decays radioactively by emitting an alpha particle (mass 6.65*10^-27) with kinetic energy 1.23*10^-12 J, as measured in the laboratory reference frame.

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.

I used the kinetic energy to solve for the velocity: k=.5mv^2 which is 19233429 m/s. Now I'm not sure what to do with that. I think I'm suppose to use the conservation of momentum theory, but I don't know how.

 

[ledhead86]

Anyone Know?

 

[whozum]

Conservation of momentum theory says that the net momentum stays constant if there are no external forces acting. Are there any external forces? What was the initial momentum?

 

[ledhead86]

No, there are no external forces. Initial momentum= mv= 19233429*6.65*10^-27= 1.27902306*10^-19

 

[ledhead86]

so does conservation of momentum not apply her? What do I need then to find the magnitude of the recoil velocity?

 

[whozum]

Before the explosion the particle is at rest. What is its momentum? No external forces means momentum is conserved.

 

[jgibbon2]

I have a problem simular to this...

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?