# Speed pf the neutron of thorin

## Homework Statement

U → Th + α

The speed of α = 6 x 105 m/s. Find the speed of neutron of Thorium!

E = mc2

momentum

## The Attempt at a Solution

I am pretty sure there is missing information, maybe the mass of α and Th. I just want to ask the way to solve it.

I thinking using the conservation of momentum. Before U decays, the total momentum is zero, so the total momentum of Th and should be zero. By knowing the mass of Th and α, we can find the speed of Th.

Is my idea correct?

And what about the speed of neutron of Thorium? Is it the same as speed of Thorium?

Thanks

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BvU
Homework Helper
2019 Award
I find it hard to believe the wording is "Find the speed of neutron of Thorium". Could you check ?

I find it hard to believe the wording is "Find the speed of neutron of Thorium". Could you check ?
Actually I got it from my friend and he said he was sure that's the exact question

Thanks

BvU
Homework Helper
2019 Award

## Homework Equations

E = mc2
I think Albert E got that right, but if you want to do a momentum balance, that's not a relevant equation!

I was thinking of using the conservation of momentum. Before U decays, the total momentum is zero, so the total momentum of Th and α should be zero. By knowing the mass of Th and α, we can find the speed of Th.
Is my idea correct?
Looks good to me. If you write it down nicely, perhaps the masses themselves are not as important as their ratio. Any "missing information, maybe the mass of α and Th" is easily found (decay chain, or: Thorium series).

And I still can't make head or tail (i.e. can't make sense) out of "speed of neutron of Thorium"

I think Albert E got that right, but if you want to do a momentum balance, that's not a relevant equation!
Yes, I am just guessing some equations related to the question :shy:

Looks good to me. If you write it down nicely, perhaps the masses themselves are not as important as their ratio. Any "missing information, maybe the mass of α and Th" is easily found (decay chain, or: Thorium series).

And I still can't make head or tail (i.e. can't make sense) out of "speed of neutron of Thorium"
The equation I think is:
mTh x vTh = mα x vα

Yes, the ratio of their masses can be used to solve the equation. I just need to look for the ratio or the mass at the booklet.

I am also not sure about the speed of neutron, maybe it is speed of Th
Thanks

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