Ballistic Pendulum: Bullet Impact at 500m/s

[rsala]

Homework Statement

a ballistic pendulum is hit by a bullet traveling 500m/s , the ballistic pendulum is a block of wood hanging from a string.
the block of wood (1kg) is hanging from the string of 2.5m
the bullet has mass .006kg @ 500m/s
the bullet passes right through the block of wood before it makes any significant movement.
the block of wood swings to a max angle of 12 degrees with the vertical.

ive drawn out a microsoft paint image.
http://img512.imageshack.us/img512/262/bulletib5.jpg

Homework Equations

conservation of energy
and momentum

The Attempt at a Solution

here is my solution
please tell me if i got the correct answer, this is from a test i took yesterday

http://img246.imageshack.us/img246/5002/bullet2lv3.jpg

edit : I've made changes,, the correct initial velocity of the block .98 m/s
and the bullets initial momentum is 3 kg-m/s
and the final bullet velocity is 333.333,, is this correct?
thank you

 

[Doc Al]

I assume the problem is to find the speed of the bullet after it passes through the block.

No, it's not correct.

(1) Recalculate a more accurate value for the change in height of the block.

(2) Recalculate the initial (post bullet) velocity of the block.

(3) Recalculate the initial momentum of the bullet. (It's not 6 kg-m/s.)

 

[rsala]

I see i made the mistake, the velocity of the block initially should be .98 m/s NOT 3.13

ic the wrong bullet momen. now, it is 3

so should the final velocity of the bullet be 333.3333 m/s?


or is it 327, ?
thank you

 

[Doc Al]

I see i made the mistake, the velocity of the block initially should be .98 m/s NOT 3.13

I get a slightly different value for the velocity.

ic the wrong bullet momen. now, it is 3

Right.

so should the final velocity of the bullet be 333.3333 m/s?

That's close to what I get.

or is it 327, ?

That's even better.

 

[rsala]

i wrote 333.333 on the test
now i don't know what to say, whether it got it wrong or not