View Single Post
  #9   Spotlight this post!  
Unread 11-02-2012, 21:37
Ether's Avatar
Ether Ether is offline
systems engineer (retired)
no team
 
Join Date: Nov 2009
Rookie Year: 1969
Location: US
Posts: 8,101
Ether has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond repute
Re: Ball launching math (with pictures!)

Quote:
Originally Posted by seg9585 View Post
Not to overcomplicate things, but a (acceleration of ball) is not a constant "g", but a summation of acceleration due to gravity, Drag, and Lift.
Yes, that's been discussed at great length here on CD.

There's a paper here that someone posted a link to a few weeks ago which discusses the effects of air friction and magnus effect, and concluded that it would be reasonable to ignore them.

I don't know whether or not I agree with that conclusion, but I suspect that even if those effects were included, other factors such as variations in ball mass, size, compressibility, surface texture, and location of center-of-mass relative to center-of-volume, and air currents and atmospheric pressure would play a role... not to mention the effect of variations from shot-to-shot in the launcher itself.

Bottom line: in this application, equations are useful for getting a ballpark estimate.

Quote:
Change in gravity is a function of Y.
You weren't seriously suggesting changing "g" with height of the ball should be considered, were you? I didn't see a smiley face at the end of that.

Quote:
calculating the final position would require iteration or an ODE solver.
With air friction and magnus included, the DE would be non-linear, and it's unlikely that an ODE solver could find a closed-form solution. The only way to solve would be numerical ("iteration", most likely rk4).

Quote:
Maybe this could be a good student summer post-build season project
I think there have been a couple of attempts already that have been posted here.