Re: OT: Looking for a good physics site
 

Why are you randomly rewriting the equation? The way to solve a quadratic equation has already been posted..

Why are you starting with a complete set of values, including time and distance, that you plug in to verify the refactored equations? Where are they coming from?

Re: OT: Looking for a good physics site
 

If you thought that was random, you need to look again. I was de-rusting my algebra skills. I know I wasn't using the method that was posted; that was not the point. I was working off the theory that if 'T' is used to solve the equation, then some permutation of the equation could be used to solve for T.

I did not start with a distance value. I calculated it. I use a complete set of values for the simple reason that I can use them to see if the refactored equation is the correct one.

Re: OT: Looking for a good physics site
 

Getting T^3 as the only factor with T out of a quadratic polynomial looks entirely random to me.

Re: OT: Looking for a good physics site
 

Google is your friend.

Looks like someone already did the work.

Re: OT: Looking for a good physics site
 

@Fyron: Hence why I need to de-rust my algebra skills. It's the circle of maaaaath...

@Jack: I did try google. More than once.

Re: OT: Looking for a good physics site
 

Well, I read it and I get the general idea...

Would these be the equations to use? (After removing the 'Z' terms)
<font class="small">Code:</font><hr /><pre>0 = ( (1/4) * (Tax2 + Tay2 + Taz2 - Pam2) ) * t4 +
( Tax * Tvx + Tay * Tvy + Taz * Tvz - Pam * Pvm ) * t3 +
( Tax * Tpx + Tvx2 + Tay * Tpy + Tvy2 +
Taz * Tpz + Tvz2 - Pam * Ppm - Pvm2 ) * t2 +
( 2 * ( Tvx * Tpx + Tvy * Tpy + Tvz * Tpz - Pvm * Ppm ) ) * t +
( Tpx2 + Tpy2 + Tpz2 - Ppm2 )</pre><hr />

<font class="small">Code:</font><hr /><pre>P't2 = ( Pam2 * Rbt2 + 2 * Pam * Pvm * Rbt + Pvm2 ) * t2 +
( 2 * Pam * Ppm * (Pam * Rbt + Pvm) - Pam2 * Rbt3 - Pam * Pvm * Rbt2 ) * t +
( (1/4) * Pam2 * Rbt4 - Pam * Ppm * Rbt2 + Ppm2 )</pre><hr />

Re: OT: Looking for a good physics site
 

Yaay, the .dll works! Thank you Jack, thank you Fyron, thank you SJ, thank you everyone else who helped!

(Now, I just have to figure out how to modify the .dll for a matching intercept...)

Re: OT: Looking for a good physics site
 

I remember now why I hate math! http://forum.shrapnelgames.com/image...ies/tongue.gif

Re: OT: Looking for a good physics site
 

Given: D = (1/2) * A * T^2 + V * T + P

T = (-V +/- Sqrt(2AD-2AP+V^2) )/A

A = 5
T = 3
P = 50
V = 15
D = 117.5

3=(-15 +/- Sqrt(2x5x117.5 - 2x5x50 + 15^2))/5
3=(-15 +/- Sqrt(1175 - 500 + 225))/5
3=(-15 +/- Sqrt(900))/5
3=( -15 +/- 30 )/5
3=( 15 or -45 )/5
3=( 3 or -9)

Also:
V = ((D-P)/T) - AT/2
P = D - (T(AT+2V))/2
A = -( (2(-D+P+TV))/T^2 )

--
Mathematica: The new calculator

Re: OT: Looking for a good physics site
 

Thanks!

Re: OT: Looking for a good physics site
 

I sent an email to MM, suggesting he read this thread. Here is his comment:
I'm guessing that he means you need different formulas for different aspects of this problem.

Re: OT: Looking for a good physics site
 

Well, I'm looking for the straight-line direction for the ship to accelerate in, at its current acceleration, to intercept another ship with the potential for both velocity and acceleration.

But I do have an (Uncommented) .dll for that now.

Re: OT: Looking for a good physics site
 

Here's a doc on missile maneuvers that seems relevant:
Proportional Navigation Against Time-Varying Target Maneuvers (pdf). It's rocket science. It's better than predecessors, but does contain a simplifying assumption: "The autopilot and seeker response is assumed to be instantaneous and the missile angle of attack is assumed to be negligibly small."

Also may be worth looking into Augmented Proportional Navigation.

Re: OT: Looking for a good physics site
 

Thanks.

Re: OT: Looking for a good physics site
 

What's a good image registration code for PHPBB2 and how would I install it? I'm getting a ton of spammers on my forum.