Hello everyone,
It's been almost a year since I made my last post and to be honest I haven't shot a slingshot for quite some time either... I've actually taken up archery - it was a toss-up between joining either my local gun club or the nearest archery club and the archery club won because it was easier to get to
![Image]()
. For those of you who are interested, I shoot a 40# English longbow.
Anyway, I wrote a program for modelling the trajectories of my arrows. The physics is reasonably simple and is explained quite well here and here. My program doesn't take into account any of the complicated flight characteristics such as the bending and rotation of the arrow, never-the-less it matches the real world data quite well and I've found it to be pretty handy on the range. Because the program ignores the more complicated characteristics of arrows, it is actually capable of computing the trajectories of spherical objects with a greater degree of precision. I thought I'd post it up here, to see if it was of any use to anyone here.
Here's a link to a copy of it that I've uploaded to my Dropbox account - I really should get myself a domain! It's a web application, so there's no need to install any software.
About the program
It uses the element to draw the graphs, which was recently introduced as part of the HTML 5 spec; this will mean that you will need a relatively modern (released < 12 months ago) browser to use it. I had to actually write my own graph-drawing library from scratch because there aren't many out there yet. I chose JavaScript - even though it is a horrible language to work with - as my platform because it executes in a sandboxed environment and doesn't force the user to download any potentially malicious binaries.
I have released all of the code under version 3.0 of the GNU GPL licence, so you're free to do pretty much whatever you like with it (with attribution please).
Instructions
Change the parameters to match those of your ammo, and then click 'Plot Trajectory'. I've put the default values to those of a 3/8" steel ball-bearing, shot at an angle of 5 degrees with an initial velocity of 80 metres/second, as an example. I'm sorry for imposing metric units on everyone!
The blue line represents the trajectory with air resistance; the red line the trajectory without air resistance, i.e. in a vacuum; and the purple line the projectile's kinetic energy, expressed as a percentage of its initial (this might be useful for hunters). To generate a copy of your graph that can be saved, click 'Generate PNG'; after it pops up you can save it by right-clicking it and selecting 'Save As…' (the exact phrase varies with different web browsers).
This was a weekend project and it's pretty rough around the edges, so there may well be bugs but please tell me what you think.
![Image]()
It's been almost a year since I made my last post and to be honest I haven't shot a slingshot for quite some time either... I've actually taken up archery - it was a toss-up between joining either my local gun club or the nearest archery club and the archery club won because it was easier to get to
Anyway, I wrote a program for modelling the trajectories of my arrows. The physics is reasonably simple and is explained quite well here and here. My program doesn't take into account any of the complicated flight characteristics such as the bending and rotation of the arrow, never-the-less it matches the real world data quite well and I've found it to be pretty handy on the range. Because the program ignores the more complicated characteristics of arrows, it is actually capable of computing the trajectories of spherical objects with a greater degree of precision. I thought I'd post it up here, to see if it was of any use to anyone here.
Here's a link to a copy of it that I've uploaded to my Dropbox account - I really should get myself a domain! It's a web application, so there's no need to install any software.
About the program
It uses the element to draw the graphs, which was recently introduced as part of the HTML 5 spec; this will mean that you will need a relatively modern (released < 12 months ago) browser to use it. I had to actually write my own graph-drawing library from scratch because there aren't many out there yet. I chose JavaScript - even though it is a horrible language to work with - as my platform because it executes in a sandboxed environment and doesn't force the user to download any potentially malicious binaries.
I have released all of the code under version 3.0 of the GNU GPL licence, so you're free to do pretty much whatever you like with it (with attribution please).
Instructions
Change the parameters to match those of your ammo, and then click 'Plot Trajectory'. I've put the default values to those of a 3/8" steel ball-bearing, shot at an angle of 5 degrees with an initial velocity of 80 metres/second, as an example. I'm sorry for imposing metric units on everyone!
The blue line represents the trajectory with air resistance; the red line the trajectory without air resistance, i.e. in a vacuum; and the purple line the projectile's kinetic energy, expressed as a percentage of its initial (this might be useful for hunters). To generate a copy of your graph that can be saved, click 'Generate PNG'; after it pops up you can save it by right-clicking it and selecting 'Save As…' (the exact phrase varies with different web browsers).
This was a weekend project and it's pretty rough around the edges, so there may well be bugs but please tell me what you think.
