What was the original speed of the bullet?

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Homework Help Overview

The problem involves a bullet colliding with a block of wood, where the bullet embeds itself into the block. The task is to determine the original speed of the bullet given the masses and the final speed of the combined system after the collision.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the conservation of momentum and the necessary equations to relate the initial and final velocities. There are attempts to set up the momentum equations before and after the collision, with some questioning the assumptions made about initial conditions.

Discussion Status

The discussion includes various attempts to clarify the momentum calculations and the roles of the involved masses. Some participants have provided guidance on writing the equations, while others have pointed out the importance of recognizing the initial momentum of the bullet.

Contextual Notes

There is an assumption that the block of wood is stationary before the collision, and participants are exploring the implications of this assumption on the momentum calculations.

Joyci116
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Homework Statement


A 10.0g bullet is fired into a stationary block of wood (m=5.00 kg). The bullet imbeds into the block. The speed of the bullet-plus-wood combination immediately after the collision is 0.600 m/s. What was the original speed of the bullet?

ball m=10.0g=0.01kg
wood m= 5.00kg
Vf=0.600m/s
Vi=?


Homework Equations


p=mv


The Attempt at a Solution


i=change in momentum
=mVi-mVf
So, solve for Vi?
Then I would have to know what i is, right?

Thank you.
 
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Write equations for the momentum before and after the collision takes place. Be sure to specify which masses are involved.
 
p=mv
The momentum found using final velocity:
p=(0.01kg)(0.600m/s)=0.006 kg*m/s (ball)
p=(5.00kg)(0.600m/s)=0.006 kg*m/s (wood)
And I assumed the initial velocity was zero, so I ended up with a zero momentum.
Is that correct so far?
 
no, the bullet started with (fast) unknown velocity
It was theonly thing that HAD momentum, at first.
 
Thanks, I finally figured it out. :D
 

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