Posted by **Confused** on Monday, December 5, 2011 at 5:02pm.

Liam fires a bullet into a block suspended by two cables, embedding the bullet in the block. The mass of the bullet is 5g and the mass of the block is 1g.

1) If the maximum height of the block is ,h, is 35 cm, how fast was the bullet originally moving?

(can you explain the steps i'm really confused)

- PHYSICS HELP MEEE SO CONFUSED -
**Anonymous**, Monday, December 5, 2011 at 5:08pm
I think there's more to this question.

Are the cables there to provide resistance to motion of the block? If so, what parameters?

Is the bullet fired straight up?

conserve momentum as the moving mass changes.

- PHYSICS HELP MEEE SO CONFUSED -
**drwls**, Monday, December 5, 2011 at 5:34pm
1) From the height H that the block+bullet rises, assuming conservation of energy for the process, calculate the initial velocity V' of the block after the bullet is embedded.

(m+M) V'^2/2 = (m+M) g H

V' = sqrt(2 g H) = 2.62 m/s

2) Momentum (but not mechanical energy) is conserved during the bullet-embedding process. If V is the initial bullet velocity,

mV = (m+M) V'

Solve for V.

m is the bullet mass and M is the block's mass.

Are you sure the block is lighter that the bullet?

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**confused**, Monday, December 5, 2011 at 9:51pm
oops its 1 kg

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