Kinetic Friction Between Block and Surface (HW Check)

[Masrat_A]

Homework Statement

A 10 g bullet is fired at 200 m/s into a 1 kg block after which they slide together 2 m on a horizontal surface. Determine the coefficient of kinetic friction between the block and surface.

Homework Equations

$M_AV_{Ai} + M_BV_{Bi} = 0$
$WNC = ΔE$

The Attempt at a Solution

$0.010(200) + V_{Bi} = 0$
$2 + V_{Bi} = 0$
$V_{Bi} = -2$

$-FKX = PE_f - PE_i$
$-M_KFNX = 0 - 1/2MV_i^2$
$-M_KMGX = 1/2MV_i^2$
$X = V_i^2/2M_Kg$
$2 = 2^2/2(10)M_K$
$20M_K = 2$
$M_K = 0.1$

Does this seem correct?

 

[kuruman]

Your first equation says that the total momentum is zero. Is the bullet not moving while the block is stationary before the collision? What's the total momentum that is conserved while the bullet becomes embedded in the block?

You need to rethink this.