Magnetic puck A, with a mass of 0.100 kg, is pushed towards stationary 0.050 kg
magnetic puck B, to cause a head-on collision. You may neglect friction. The initial
velocity of puck A is 12 m/s [E]. Puck B moves with a velocity of 14 m/s [E], after
a) Find the velocity of puck A after the collision.
Einitial = Efinal
Ek = 1/2mv^2
The Attempt at a Solution
Basically I understand how to solve the question using the momentum by why is that I get a different velocity when using the energy?
Since friction is neglected, where could this system be losing kinetic energy?
I did Ei=Ef which is Eki=Ekf
1/2(0.100)(12)^2+0=1/2(0.100)v_A^2 + 1/2(0.050)(14)^2
I end up getting 6.8m/s for the final velocity of puck A
But the correct answer is 5.0m/s
I tried to plug that into the equation but I get
7.2J=6.15J which is incorrect. What am I doing wrong here?