Determining Final Velocity in 2-Dimensional Collision Problem

[dnawiam]

Homework Statement

A neutron of mass 1.7 X 10^-27 kg traveling at 2.2 km/s, hits a stationary helium nucleus of mass 6.6 X 10^-27 kg. After the collision, the velocity of the helium nucleus is 0.53 km/s at 52° to the original direction of motion of the neutron. Determine the final velocity of the neutron.

Homework Equations

pi1x+pi2x=pf1x+pf2x
pi1y+pi2y=pf1y+pf2y

The Attempt at a Solution

I changed all the km/s to m/s since the answer is in m/s

(1.7X10^-27(2200)-6.6X10^-27(530cos52))/1.7X10^-27=vficos∅
933.18m/s=vficos∅

Well, it does not matter what i get for the y component since the answer 1.9 m/s and 933 is just too high.
So, is the answer wrong or did i do something wrong.

 

[TSny]

I think the answer you were given should have been 1.9 km/s rather than 1.9 m/s.

 

[dnawiam]

Well, I did solve it for km/s I got 1.05 km/s.
vf2y=0.53sin52
vf2y=0.418km/s
vf2x=0.933 km/s

If you use the Pythagorean theorem you get 1.05km/s

 

[TSny]

Well, I did solve it for km/s I got 1.05 km/s.
vf2y=0.53sin52
vf2y=0.418km/s

You did not account for the masses of the particles in this calculation.

 

[dnawiam]

You did not account for the masses of the particles in this calculation.

You are right. How silly of me. Well, I got 1.9 km /m for my answer. Thanks for your help.