Posted by **Please Help!** on Sunday, November 21, 2010 at 11:46pm.

An alpha particle collides with an oxygen nucleus, initially at rest. The alpha particle is scattered at an angle of 60.9° above its initial direction of motion, and the oxygen nucleus recoils at an angle of 51.9° on the opposite side of that initial direction. The final speed of the nucleus is 1.32 105 m/s. In atomic mass units, the mass of an alpha particle is 4.0 u. The mass of an oxygen nucleus is 16 u.

(a) Find the final speed of the alpha particle.

m/s

(b) Find the initial speed of the alpha particle.

m/s

- physics -
**drwls**, Monday, November 22, 2010 at 12:26am
The final momentum components of the two particles perpendicular to the initial direction must cancel. Therefore

1.32*10^5*sin51.9 = Va'*sin60.9

Solve for Va', the final speed of the alpha particle.

Get the initial speed of the alpha particle, Va, by applying conservation of momentum to the intial direction of motion.

Va*4 = 16*1.32*10^5*cos51.0 + 4*Va'*cos60.9

You know Va' from part a. Solve for Va

- physics -
**Please Help!**, Monday, November 22, 2010 at 2:52am
I tried this and got

118882 for Va'

and 390097 for Va

but it was wrong?

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