Coefficient of friction - bullet traveling through a block

[mybrohshi5]

Homework Statement

A bullet with a mass of 7.00 g is fired horizontally with a speed of 420 m/s, into a wooden block with mass of 0.820 kg, initially at rest on a level surface. The bullet passes through the block and emerges with its speed reduced to 130 m/s. The block slides a distance of 47.0 cm along the surface from its initial position.

What is the coefficient of kinetic friction between block and surface?

Homework Equations

vf²=vi²+2ad

F=ma

u_k = f_k/n

The Attempt at a Solution

I found the acceleration of the bullet

130²=420²+2a(.47)

a= -169680.8

i then thought i could find the force and then divide that by the normal force to get u_k but my number was very large (141) :(

Can anyone help me on this one please.

Thank you :)

 

[Filip Larsen]

Think about if you perhaps can use conservation of momentum to analyze your problem.

 

[mybrohshi5]

Got it. That worked perfectly. Thank you i appreciate it :)