# Solving for a variable in a constant acceleration equation

• Apr 22nd 2010, 07:26 PM
HyperKaehler
Solving for a variable in a constant acceleration equation
My brother in middle school recently asked me to solve the following physics equation for t:

$d = v_it + \frac{1}{2}at^2$

For some reason my brain is going dead and I can't figure out if this equation is solvable. I've tried to solve it but my algebra is rusty. Do you need a second equation to determine t? Thanks a lot!
• Apr 22nd 2010, 08:12 PM
pickslides
You can solve for $t$ by completing the square.

Can you remember how this goes?
• Apr 22nd 2010, 08:23 PM
HyperKaehler
Wow, I'm an idiot. I didn't even realize that it was a quadratic equation. I was just looking at it trying to factor out t. Thanks a lot!