Need help with projectile motion problem

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Discussion Overview

The discussion revolves around a projectile motion problem involving the launch of a pumpkin at a specific distance during a competition. Participants explore the necessary information to determine the muzzle velocity, considering various factors such as launch angle and air resistance.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant notes the lack of sufficient information to solve for the muzzle velocity, highlighting the need for two of the three variables typically required in range formula problems.
  • Another participant mentions that there is an optimal angle for maximum range, suggesting it is understood that the pumpkin was launched at this angle.
  • It is proposed that the optimal angle for maximum range in a vacuum is 45 degrees, while in the presence of air resistance, it ranges between 30 and 45 degrees.
  • A participant references a book on ballistics, indicating that the equations may not apply to objects with the low ballistic coefficient of pumpkins, suggesting numerical methods might be necessary.
  • One participant shares an anecdote about shotgun testing at a 30-degree elevation, noting the unexpected behavior of the pellets, which adds a personal narrative to the discussion.
  • Another participant humorously comments on the anecdote, speculating about the relationship dynamics involved, while also acknowledging the ethical considerations of the situation.

Areas of Agreement / Disagreement

Participants express differing views on the assumptions necessary for solving the problem, particularly regarding the launch angle and the effects of air resistance. The discussion remains unresolved with multiple competing perspectives on how to approach the problem.

Contextual Notes

Participants acknowledge the limitations of the assumptions made, particularly the neglect of air resistance and the specific characteristics of the projectile (pumpkin) impacting the applicability of standard equations.

kwaber1
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I found this interesting problem on the internet, but I think there is not enough infromation to solve.
"At the 1998 Punkin Chunkin World Championship, a pneumatically-driven device called the "Aludium Q36 Pumpkin Modulator" was able to project a 3.6-4.5 kg (8-10 pound) pumpkin intact for a total distance of 1227.23 m (4026.32 feet, how many feet are in a mile?). What was the muzzle velocity (magnitude and direction) of the record-setting pumpkin?"

Most range formula problems give you 2 of the 3 variables to solve for the third R, vo or Θ
Any help would be appreciated.
 
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Neglecting the effects of friction (a necessary but absurd assumption) there is a value of ##\theta## that gives you the maximum range. I think it's understood that the pumpkin was chucked at this angle.
 
The optimal angle for maximum range in a vacuum is 45 degrees. When the effect of air resistance is included, it's between 30 and 45 degrees.

The definitive book on the subject is Modern Practical Ballistics, by Arthur J. Pejsa. The equations in that book may not cover objects with the (low) ballistic coefficient of pumpkins. If so, numerical methods are needed.

For a shotgun with birdshot fired at (very roughly) 30 degree elevation, the pellets come almost straight down at maximum range. This from a test where my dad had my mother shoot at him. Unfortunately, she had no experience with a double barrel shotgun with double triggers, so she fired both barrels at the same time and got knocked down from the recoil. That ended further testing.
 
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JRMichler said:
For a shotgun with birdshot fired at (very roughly) 30 degree elevation, the pellets come almost straight down at maximum range. This from a test where my dad had my mother shoot at him. Unfortunately, she had no experience with a double barrel shotgun with double triggers, so she fired both barrels at the same time and got knocked down from the recoil. That ended further testing.

This is a fascinating report. One could speculate all day about your parents relationship (lol!). Considering the legal/moral/ethical aspects of this situation, it is probably best that testing ended at that point.
 

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