A bullet strikes a wooden block

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Homework Help Overview

The problem involves a bullet striking a wooden block, where the bullet becomes embedded in the block. The scenario includes calculating the height to which the combined mass swings after the collision. The subject area pertains to momentum conservation and energy principles in mechanics.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to apply conservation of momentum and energy principles to determine the height after the collision. Some participants question the relevance of the string length in relation to the height calculation.

Discussion Status

Participants are exploring the implications of the string length on the problem and discussing the appropriateness of the calculations made by the original poster. There is a mix of affirmation regarding the calculations and inquiries about the role of the string length.

Contextual Notes

There is a mention of potential constraints regarding the string length and its impact on further calculations, such as maximum angle or oscillation frequency, which are not directly addressed in the original problem statement.

Arooj
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Homework Statement


A 25 g bullet is fired at 150 m/s into a 2.0 kg block of wood hanging from a string 3.0 m long. The bullet becomes embedded in the block. To what height do the bullet and block swing?


Homework Equations


m1v1 = (m1+m2)vf
1/2 mv^2 = mgh



The Attempt at a Solution


0.025 (150) = (0.025 + 2)vf
vf = 1.85 m/s

1/2 2.025 1.85^2 = 2.025 9.8 h
h = 0.175 m

I don't know what to do from here.
 
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First things first, try not to plug in numbers until after you get the final result. This reduces rounding error and can give you let you see how to do some of the algebra without having to deal with specific numbers.
That being said, you seem to have done everything right. What do you mean "I don't know that to do from here." You were told to find the height and you found the height.
 
So the length of the string doesn't matter?
 
Yes. It would only matter if the height is more than twice the string length. If it then wants you to calculate the maximum angle or the oscillation frequency, then the string length would also matter.
 

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