Impulse

[brad sue]

Hi,
I would like to have some help the following problem
If a 32 g arrow moving at 160km/h penetrates a block of wood suspended by a rope, what is the impulse is delivered to the block?
The impulse= momentumfinal-momentuminitial.
We know that momentuminitial= 0.32 kg* 44.44m/s=14,28 N.
But what is the momentumfinal??
I do not understand this concept well even after read the texbook. Can someone explain me what is going on ?
Thank you
B

[Diane_]

I think the question is poorly written, as whether it can be solved or not depends on the definition of the word "penetrates". To me, that means it passes through the block and continues on - in which case, there isn't enough information to solve the problem uniquely.

So we'll make the other assumption - that the arrow simply sticks in the block. In this case, there is only one object after the collision occurs. Do you see a way to determine the velocity of that object? Think conservation.