# Physics Particle Decay Question (Cons. of Momentum?)

1. Oct 20, 2013

### jlewallen18

Physics Particle Decay Question (Cons. of Momentum??)

1. The problem statement, all variables and given/known data
An isotope of Polonium 210Po with mass 3.49x10^-25 kg can decay into an alpha-particle(He Nucleus) with mass of 6.64x10^-27 kg and an isotope of lead 206Pb with a mass of 3.42x10^-25. If the polonium decays at rest. and the final decay products have a total KE of 8.65x10^-13 J, what are the speeds of the He and Pb nuclei?

2. Relevant equations

(m1+m2)Vo = m1v1 + m2v2

3. The attempt at a solution

My first thought was to plug in what was given but then I get stuck...

(Po)(0) = (He)(V_He) + (Pb)(V_Pb)

That gets me nowhere.

It's multiple choice

A. 0.17 m
B. 0.15 m
C. 0.08 m
D. 0.03 m
E. 0.00 m

I wish I could show more work, I just dont know where to go with it at all

2. Oct 21, 2013

### Simon Bridge

All conservation of momentum problems have the same pattern.

step 1. sketch the situation "before" ... in this case you have a Po nucleus.
... draw on the momentum arrow and label it ... in this case, what is the initial momentum?

step 2. sketch the situation "after" ... in this case you have two particles.
... which directions to they head off in (compared to each other)?
... draw the momentum arrows and label them. Leave variable names for anything you don't know.

Is there a relationship between kinetic energy and momentum you can exploit?

Step 3. total momentum before = total momentum after.