Physics Help!

[DrPizza]

Darn it... something's not checking out. I must have also made some sort of mistake somewhere.
darn it darn it darn it. I'm also on 4 hours of sleep.

Sorry, I'd stay up later and find my mistake, but I'm exhausted. The basic small steps I outlined are correct... but there's a careless mistake there somewhere.

 

[allies]

hahah yea i'm not getting the answer, even with your help... i think i should jsut go to bed :\

 

[DrPizza]

Perhaps if I actually used a piece of paper, instead of just typing as I went, I wouldn't have a mistake.

 

[DrPizza]

yeah, everything checks.

it's all fine now.
the equation for a became after fixing that one error,

18a + 4(18a - 19.6) = 5300
a = 23 m/s/s

Check
After 18 seconds, velocity = 413.7 m/s
divide by 2 for average velocity and multiply by the 18 seconds = displacement of 3723.5 m

from 18 to 22 seconds, velocity goes from 413.7m/s to 413.7m/s minus 4s*9.8 m/s/s
divide by 2 for average velocity over those 4 seconds
multiply by the 4 seconds, and the displacement there equals 1576.5 meters.

add 1576.5 meters and 3723.5 meters.
BAM. 5300 meters.

20 seconds with pen and paper... 30 minutes when I was typing it. Typing math sucks.