Uhh.... I am making this little game involving a physics engine... and i forgot my formulas... and I can't find them on the web... what is the formula to find out the time taken for a straight line journey, if you know the constant acceleration and distance? I have 'worked out': time=sqrt(distance/acceleration) but it doesn't seems to be quite right... any help?

your forumla for time is correct.

ummm...giyf

anyway, 0.5*a*t^2=d, so t = sqrt(2.0*d/a)

v = u + at
s = vt

u (initial velocity) = 0
s = a * t * t
t = sqrt(s/a)

Nope, you need calculus to do that correctly. DoG is right.

s'' = a
s' = v1 + a*t
s = s1 + v1*t + (a*t^2)/2

Ignoring displacement in general, or the intial velocity, you get d = (a*t^2)/2.

*sigh* it can all be done without calculus

v = u + at
s = 1/2 * (u + v) * t

u (initial velocity) = 0
s = 1/2 * v * t * t
t = sqrt(2*s/a)

its been too long since I did physics

Not to drag this on, but I'd like to point out that s = (u + v)*t/2 is using calculus. It's finding the area under the trapzoid in the velocity graph to determine the displacement.

Yes, but all these forumla can be derives without calculus..

Newton developed these equations before he invented calculus.

v[bar] = s / t
v[bar] = average velocity = 1/2 ( u + v )

Even if he didn't call it calculus back then, it is still calculus.

uhh... Thanks guys....

(notices that unknown has 1337 posts under is belt.)

Yep, no problem. We always enjoy bickering over questions.

Skorche Wrote:Not to drag this on, but I'd like to point out that s = (u + v)*t/2 is using calculus. It's finding the area under the trapzoid in the velocity graph to determine the displacement.

Yes, but in this case u=0 so the formula is really finding the area under a triangle.
Even when u != 0, the formula can be derived using the quadratic formula. Would you consider that calculus?

Whoa, I looked into my notebook and found this:
d = ut + 1/2at² therefore
0 = 1/2at²+ut-d using the quadratic formula yields:
t = (-u + sqrt(u² + 2ad)) / a


Can this be simplified or something?

P.S. I don't think I used Calculus

---------------------
I'm confused

I don't believe that can be simplified any further.

Once again, while you didn't use any calculus, the formula d = ut + 1/2at² is derived using ideas from calculus.

yeah but the idea of v-bar, average time for an entire journey is not derived from calculus, neithe was anything in my post. (the one that I didnt make a stupid mistake in that is)