To what depth will the bullet penetrate the block in this case?

[frosti]

Homework Statement

A 7.00 g bullet, when fired from a gun into a 1.00 kg block of wood held in a vise, penetrates the block to a depth of 7.60 cm. This block of wood is next placed on a frictionless horizontal surface, and a second 7.00 g bullet is fired from the gun into the block. To what depth will the bullet penetrate the block in this case?

Homework Equations

m1v1 + m2v2 = (m1+m2)vf

The Attempt at a Solution

I have no clue how to solve this problem. I don't really know what to do with the depth of penetration by the bullet. Can anyone please help?

 

[PhanthomJay]

Homework Statement

A 7.00 g bullet, when fired from a gun into a 1.00 kg block of wood held in a vise, penetrates the block to a depth of 7.60 cm. This block of wood is next placed on a frictionless horizontal surface, and a second 7.00 g bullet is fired from the gun into the block. To what depth will the bullet penetrate the block in this case?

Homework Equations

m1v1 + m2v2 = (m1+m2)vf

The Attempt at a Solution

I have no clue how to solve this problem. I don't really know what to do with the depth of penetration by the bullet. Can anyone please help?

There's a significant loss of KE in part 1...like all of it, 1/2mv_b^2. In part 2 , apply conservation of momentum, and determine the total loss of KE. It' ll be a bit less; how does that ratio difference relate to the new depth of penetration?