OT: Looking for a good physics site

[Fyron]

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?

[narf poit chez BOOM]

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.

[Fyron]

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

[narf poit chez BOOM]

@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.

[narf poit chez BOOM]

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

Would these be the equations to use? (After removing the 'Z' terms)
Code:

---

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 )

---

Code:

---

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 )

---

[narf poit chez BOOM]

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...)

[AngleWyrm]

narf poit chez BOOM said: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.

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

[narf poit chez BOOM]

Thanks!

[Baron Munchausen]

I sent an email to MM, suggesting he read this thread. Here is his comment:

They're on the right track, but the basic problem is not spelled out. Is
this person looking for the intercept point, or angle and velocity for one
of the ships? If this is a missile seeking against another, are their
restrictions on the missile's movement? He needs to provide quite a bit more
information.

I'm guessing that he means you need different formulas for different aspects of this problem.

[narf poit chez BOOM]

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.