Finding the speed of a bullet via device with two rotating disks

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Homework Help Overview

The problem involves a device with two rotating disks, separated by a distance, through which a bullet passes. The angular speed of the disks and the angular displacement between the bullet holes are provided, and the goal is to determine the bullet's speed.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants are discussing the arrangement of the disks and the relationship between distance, time, and speed. Questions about the setup and the equations being used are raised, along with considerations of how to relate the known variables to find the bullet's speed.

Discussion Status

The discussion is ongoing, with participants exploring the problem's setup and the relationships between the variables. Some guidance has been offered regarding the mathematical relationships involved, but no consensus or resolution has been reached yet.

Contextual Notes

There is a request for clarification on the arrangement of the disks and the equations being utilized, indicating that further information may be needed to fully understand the problem.

TmrK
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Homework Statement


The device consists of two rotating disks, separated by a distance of d = 0.879 m, and rotating with an angular speed of 96.1 rad/s. The bullet first passes through the left disk and then through the right disk. It is found that the angular displacement between the two bullet holes is θ = 0.161 rad. From these data, determine the speed of the bullet.

Basically, I'm lost in this equation.
 
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What do you mean left disk, then right disk? How are the disks arranged? Are they both turning on the same shaft one behind the other? A sketch would be informative. Also, please show what equations you are working with.
 
θ=s/r & w=Δθ/Δt & α=Δω/Δt
 

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OK, let's get started thinking about this problem.

What do you know about distance, time, and speed? How are they related mathematically?

You know how fast the disks are turning and therefore know how long it takes to make one complete revolution. You know how much the disks turned between bullet holes. You know the distance between the disks.

This data can be related to determine the speed of the bullet. Let's see how you put it all together to solve the problem.
 

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