Re: Nerf ball starting at 12m/s 45 degree angle ending at 8ft 6in w/ air resistance
 

Just curious.. where did you find this?

Re: Nerf ball starting at 12m/s 45 degree angle ending at 8ft 6in w/ air resistance
 

Taken from Section 4 - The Game

<S02> Muzzle Velocity - No ROBOT may throw a ball with an exit velocity of greater than 12 m/s (26.8 mph).
As a reference, a ball traveling at this velocity when leaving the ROBOT at an angle of 30º from
horizontal with no spin will travel approximately 35 feet. A robot that violates this rule will be
considered unsafe per <S01>.

Re: Nerf ball starting at 12m/s 45 degree angle ending at 8ft 6in w/ air resistance
 

And the mean, mode and standard deviation? I also want to see a scatter plot to check to see if it is a one-tail or two-tail population, or even one with more than one mode. Some sort of 3D modelling of mass density would be nice, too.

Re: Nerf ball starting at 12m/s 45 degree angle ending at 8ft 6in w/ air resistance
 

I massed 6, using a mean of .18 ... the mass deviations dont significantly affect the range..

Re: Nerf ball starting at 12m/s 45 degree angle ending at 8ft 6in w/ air resistance
 

When I posted this all I wanted was that distance. So we can make a "no one can shoot past here arc" on our field.

Re: Nerf ball starting at 12m/s 45 degree angle ending at 8ft 6in w/ air resistance
 

oh, is THAT what you want?

I think that's 6.5 meters. well, I'll just generate the full table and find the max, faster that way =p.

*edit* - wow, finals studying is making me drowsy.. but the max should be around 8.8 meters.. give or take maybe .5 meters.. (sorry, I dont have a full lookup table, but this seems pretty close..)

*edit 2* - does anyone still want the lookup tables?

Re: Nerf ball starting at 12m/s 45 degree angle ending at 8ft 6in w/ air resistance
 

I might if I knew what they were... all I know that I need is that one length, what will that table give me?

Also, is there any way to calculate what the best angle would be instead of 45 degrees?

Re: Nerf ball starting at 12m/s 45 degree angle ending at 8ft 6in w/ air resistance
 

Well, a standard lookuptable is something like this..

y axis - theta
x axis - v

the entry for some v and theta gives you the distance (in this case from 5 ft to 81/2 ft).. therefore you reverse-lookup to find a theta. Lets say you keep v constant at 12 m/s Now just find an entry in the table which is equal do your distance from the goal... that gives you your fireing angle. Fire.

Otherwise you have to calculate angle depending on your distance, that's not possible when you factor air resistance.. (at least not to my knowelege).. so you have 2 options

a). use lookup tables to find an angle that matches your distance

or b). use a model without air-resistance and be off by a large amount the farther away you get.

Either way its not pretty, but I think our team wants to do a). (psst.. dont tell them I already made the lookup table, I want to see how fast our programmers get it =p )

Re: Nerf ball starting at 12m/s 45 degree angle ending at 8ft 6in w/ air resistance
 

LoL! So mean... so mean....

Re: Nerf ball starting at 12m/s 45 degree angle ending at 8ft 6in w/ air resistance
 

Here is a picture that show a theoretical max distance. It ignores the effects of drag and spin.
It shows the theoretical max distance, when the ball is launched from ground level, at 12m/s and 45 deg. elevation to be about 37.2 ft/11.34m.

Re: Nerf ball starting at 12m/s 45 degree angle ending at 8ft 6in w/ air resistance
 

In another thread, I posted a link to a paper that describes how to calculate the trajectory of a ball, including air resistance. I also attached an Excel file that allows the user to vary launch speed, angle and height as well as ball mass, diameter, drag coefficent. It produces a trajectory plot with the upper and lower heights for the goal shown on the graph. It's pretty easy to use and gives you a tool to determine how sensitive the trajectory is to the various parameters.

See:
http://www.chiefdelphi.com/forums/sh...710#post429710

Re: Nerf ball starting at 12m/s 45 degree angle ending at 8ft 6in w/ air resistance
 

Im no math whiz, but would this work? have your launcher (for instance turret like a snowblower) and mount the cam so its on the top of the launcher, then proportionally program the offset of cam-turret to greenlight-hole? that way when your bot drives the cam always tracks the greenlight and your launcher is always aimed there. Me=mechanical and not too electrically intuitive, is this possible?

Re: Nerf ball starting at 12m/s 45 degree angle ending at 8ft 6in w/ air resistance
 

By the way billbo911's calculations were provided by:
www.hyperphysics.phy-astr.gsu.edu

We got:
From 1.4 meters off ground to center of goal, we calculated that max range 11.1 meters at 48 degrees. That includes drag coefficient of 0.3 - constant drag coefficient. The proof is left for an exercise for the reader. :D

Re: Nerf ball starting at 12m/s 45 degree angle ending at 8ft 6in w/ air resistance
 

How'd you get that number? you're off about 3 meters from my calculations.. weird. want to run your caclulations again with a coefficient of .416 (should be more accurate)? I might be wrong..

Re: Nerf ball starting at 12m/s 45 degree angle ending at 8ft 6in w/ air resistance
 

Air resistance is not a factor unless you are going 75+ mph. So you dont have to account air resistance into the equation.