So I have the formula and values substituted in correctly - but now the simple algebra part is killing me.

x = vt + 1/2at^2

.06=(2*10^3)t + 1/2(4*10^7)t^2

What is t?

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- Aug 9th 2010, 06:53 PMjessegarwoodPhysics Kinematics Equation Must Be Solved W/ Algebra
So I have the formula and values substituted in correctly - but now the simple algebra part is killing me.

x = vt + 1/2at^2

.06=(2*10^3)t + 1/2(4*10^7)t^2

What is t? - Aug 9th 2010, 07:09 PMeumyang
$\displaystyle .06 = (2*10^3)t + 1/2(4*10^7)t^2$

$\displaystyle .06 = 2000t + 20000000t^2$

Set equal to 0 and rearrange:

$\displaystyle 20000000t^2 + 2000t - 0.06 = 0$

Use the quadratic formula:

$\displaystyle \begin{aligned}

t &= \dfrac{-2000 \pm \sqrt{2000^2 - 4(20000000)(-0.06)}}{2(20000000)} \\

&= \dfrac{-2000 \pm \sqrt{4000000 + 4800000}}{40000000} \\

&= \dfrac{-2000 \pm \sqrt{8800000}}{40000000} \\

&\approx 2.42 \times 10^{-5}, -1.24 \times 10^{-4}

\end{aligned}$ - Aug 9th 2010, 07:11 PMTKHunny
Yikes! You should have studied Quadratic Equations over the previous years.

If you write it like this: ½at^2 + vt - x = 0, you should find solutions from the Quadratic Equation, or Completing the Square. Ringing any bells, yet?