How to Calculate Frictional Force and Time for a Bullet Penetrating Wood?

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Homework Help Overview

The discussion revolves around calculating the frictional force and the time it takes for a bullet to come to rest after penetrating wood. The problem involves a bullet with a specified mass and initial velocity, and it raises questions about the application of physics principles such as the work-energy theorem.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • The original poster attempts to apply the work-energy theorem to determine the frictional force but expresses uncertainty about the method to find the stopping time. Other participants question the assumptions made regarding the constancy of force and acceleration.

Discussion Status

Participants are exploring different approaches to the problem, with some guidance offered regarding the use of the work-energy theorem. There is an acknowledgment of a discrepancy in the calculated time, and the discussion includes references to expected answers from a textbook, indicating multiple interpretations of the problem.

Contextual Notes

There is mention of a specific answer from a textbook, which suggests a potential constraint or benchmark for the calculations being discussed. The original poster also notes frustration with the problem-solving process, indicating a lack of clarity in their approach.

brick06
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A 10 gram bullet with a horizontal speed of 400m/s hits a block of wood and penetrates 12 cm.
a. what is the frictional force?
b.how long does it take the bullet to come to rest

I have the answers but cannot figure out how to get there. I set my initial velocity to 400 m./s, making my final velocity 0... any help would be great, I am going nuts.
 
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Do not ever double post!
Let the moderators take care of misplaced post.
I've given you a hint in your first thread.
 
okay i used the work energy theorem to find the friction force,and my other thread has disappeared. So what should i use now to find the time it takes to stop, when i tried i got 12 seconds, but that does not seem right whatsoever
 
btw the back of the book says the answer should be 600 mu seconds
 
Well, assuming the forceyou've found is constant over time, what acceleration does it induce?
 

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