Acceleration of a pumpkin from an air cannon

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Discussion Overview

The discussion centers around the acceleration of a pumpkin launched from an air cannon, particularly focusing on the complexities involved when air pressure is not constant. Participants explore the theoretical and practical aspects of pumpkin chunking, including equations of motion and the effects of air resistance.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant mentions the fundamental equation f=ma but notes the complexity in determining the force (f) involved in launching the pumpkin.
  • Another participant expresses skepticism about the usefulness of an analytic approach for pumpkin chunking, suggesting that experimentation and observation may yield better insights.
  • A participant shares a link to a calculator designed for pumpkin chunking, proposing that the launch force could be considered constant across shots, allowing for calibration based on measured data.
  • Concerns about air drag affecting the trajectory of the pumpkin are raised, indicating that the pumpkin's non-point particle nature complicates the motion analysis.
  • Several participants suggest using equations related to projectile motion, particularly those that account for air resistance, as potential content for a t-shirt design.

Areas of Agreement / Disagreement

Participants express a mix of agreement on the need for experimental approaches while also presenting differing views on the applicability of theoretical equations. The discussion remains unresolved regarding the best methods to analyze the pumpkin's acceleration.

Contextual Notes

Participants acknowledge the limitations of their approaches, including the dependence on accurate measurements of the pumpkin's weight and launch angle, as well as the unresolved nature of the equations involved in the analysis.

Who May Find This Useful

This discussion may be of interest to those involved in experimental physics, engineering, or anyone participating in pumpkin chunking events, as well as educators looking for practical applications of projectile motion concepts.

philip porhammer
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Summary: what is the equation for a pumkin's acceleration when the air pressure in not constant.

My Daughter and I are going to Pumpkin chunkin for the first time.
I would like to get two orange shirts and scribble:
what part of this don't you understand:
(DifEq?) acceleration of a pumpkin from an air cannon. acceleration is not constant.
I will draw out an air cannon. this is only for my daughter and I. not making any for sale. just having fun!
will post a pic here from the event...
 
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philip porhammer said:
Pumpkin chunkin
Good for you. That sounds like a great activity for father and daughter.

The first principle equation is the familiar f=ma. But the devil is figuring out what f is. You'll find that it is not a simple formula, but a long list of equations with unknown coefficients.

I am very skeptical that the analytic approach will be much help with pumpkin chunkin. Learn from others; watch lots of Youtube videos; experiment. There is still lots of room for experimental physics/engineering in this world.
 
air cannon theory has good equations! thanks!
 
Like so many things today, there's a tool for this and an app for that. In this case, there's a calculator for pumpkin Chunkin:

http://www.iconico.com/ultimaCalc/punkin_balllistics.aspx
First I imagine the launch force will be constant for all pumpkin shots so that means that by measuring a few shots you could get the equations calibrated. From there, knowing the weight of the pumpkin (can you weigh it?) and the angle of the shot you could figure the distance. Also remember that since the pumpkin isn't a point particle that there is air drag that will blunt the parabolic trajectory of a perfect shot.
 
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I just looking to make a t-shirt for my daughter and I with some equations and an air cannon, thantks
 
But wouldn't it be cooler to actually win and then you could sell tons of the t-shirt that made it all possible. :-)
 
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wiki "projectile motion"

scroll down to the section
Trajectory of a projectile with air resistance

Look for equations sx (this is the horizontal distance reached). That ought to be good enough for a tee shirt
 
Here's some slides with projectile motion and graphs for your t-shirt (just add a pumpkin somewhere):

tra4.gif


http://hydrogen.physik.uni-wuppertal.de/hyperphysics/hyperphysics/hbase/traj.html
 

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