Physics
posted by Kelly .
The collision between a hammer and a nail can be considered to be approximately elastic. Estimate the kinetic energy acquired by a 13 g nail when it is struck by a 550 g hammer moving with an initial speed of 4.0 m/s.
I solved for the final velocities of both and got 3.8 m/s for the hammer and 8.46 m/s for the nail.
How do I get my final answer.. I'm so close! haha

Ki = (.5*mass of hammer*vi^2)
Kf = (.5*mass of hammer*vf^2)
* you should add the Kf of the nail too, but for me it was near negligible.
KiKf = :] 
Calculate the kinetic energy acquired by a 15g nail when it is struck by a 600g hammer moving with an initial speed of 4.1m/s .