Calculating Vertical Momentum Conservation in a Collision

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Homework Help Overview

The discussion revolves around a momentum conservation problem in a vertical collision scenario involving a bullet and a block of wood. The original poster seeks to determine how high the block rises after the bullet embeds itself in it, given specific masses and initial velocities.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • The original poster calculates initial momentum and velocity but struggles with finding the height the block reaches. Some participants suggest considering mechanical energy conservation post-collision, while others question the need for a defined starting height.

Discussion Status

Participants are exploring different interpretations of the problem, with some guidance provided regarding the definition of the coordinate system. The original poster indicates a resolution to their confusion, suggesting a productive direction has been established.

Contextual Notes

The original poster expresses uncertainty about the starting height of the block, which is a crucial aspect of the problem. There is also mention of an upcoming exam, indicating time constraints and the need for clarity on related concepts.

metalmagik
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Hello, I do not know how to do this momentum conservation problem in the vertical direction, when the object is to find how far the second object went.
A gun is fired vertically into a 1.40-kg block of wood at rest directly above it. If the bullet has a mass of 21.0g (.021 kg) and a speed of 210 m/s, how high will the block rise into the air after the bullet becomes embedded in it?
I have found momentum which was 44.1 kgm/s and the velocity of the block which was 3.15 m/s but I just do not know how I would find the distance the block traveled. The answer is .491 m. Quick help is appreciated, thank you.
 
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HINT: After the collision, mechanical energy is conserved.
 
I'm still a little confused, I've tried doing mgh = 1/2mv^2 + mgh but I realized I do not have the starting height...I am lost to what else I am supposed to do regarding this problem.
 
Just define your coordinate system so that the starting height of the block (i.e. the height of the table, or whatever it's on) is zero. Then when you solve for h that will be the height it reached off the table.
 
Thank you, I have solved this problem, it was really just a simple interpretation problem on my part, thanks again, I have one more question I do not quite understand that I expect to see on my exam tomorrow, I will post it in a new thread called "Momentum Particles" if anyone is kind enough to help me with it before the end of tonight.
 

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