A 60-g bullet fired at two blocks resting on a surface with coefficient of kinetic friction =0.5.

Question

The bullet pass through a 8-kg block and make this block slides 0.8 m.
And then the bullet lodges in another block which is 6 kg. The bullet make it slides 1.2 m.

Here is where i got lost, i list two equation:
m-mass of bullet
M-mass of 8-kg block
Vi-initial velocity of bullet
Vf-final velocity of the bullet & 8-kg-block
fk-frictional force acting on the bullet & 8-kg-block

m*Vi=(m+M)Vf
1/2(m+M)(Vf)^2=fk*d

I think all the work of the frictional force equals to the energy provided to the block by the collision
Where did i go wrong?

Answer 1

Collision is inelastic
Energy cannot be conserved!!!