The Student Room Group

Scroll to see replies

Reply 1
Make LHS=0 and use the quadratic formula
Reply 2
...
Reply 3
SyedT
s= ut + 0.5at^2

s = t^2(u/t + 0.5a)

s/t^2 = u + (0.5a)/t

t^2 = st/ (u + 0.5a)

t = s/(u+0.5a)


what's happening in that step?
If your trying to say that you've gone from
(u/t + 0.5a)
to
(u+0.5a)/t

then that's wrong.
^ wrong. I don't think you can do it.
Reply 5
TI-84
what's happening in that step?
If your trying to say that you've gone from
(u/t + 0.5a)
to
(u+0.5a)/t

then that's wrong.


Sorry about that,I made an error,I've edited my post.
2nd order polynomial in t, use quad formula
Reply 7
You can't do it.
Reply 8
surely its just +-sqrt((2(s-ut))/a)) = T
Reply 9
shawrie777
Make LHS=0 and use the quadratic formula


+1
Reply 10
cambo211
surely its just +-sqrt((2(s-ut))/a)) = T


oh wait
just realised t in UT

stupid me

but anyway

0 = 1/2at^2 + ut - s

then T = (-u +/- sqrt(u^2 + 2as))/a
Reply 11
lolhenry
(2s)/(u+at)=t[br][br]or[br][br]t=ut±((ut)22s)(2s)/(u+at)=t[br][br]or[br][br]t = -ut \pm \sqrt((ut)^2-2s)


which is what i did first but then you havnt got it in terms of t because you have t in both sides
Reply 12
I made the LHS =o and completed the square and came to:

t= (-u +or- the square root of (2sa+u^2))/a

which is: -u plus or minus the square root of (2sa + u squared). Everything over a.

Is that right?
Reply 13
AarenHealy
I made the LHS =o and completed the square and came to:

t= (-u +or- the square root of (2sa+u^2))/a

which is: -u plus or minus the square root of (2sa + u squared). Everything over a.

Is that right?


Yes :smile:
Reply 14
cambo211
which is what i did first but then you havnt got it in terms of t because you have t in both sides


Meaning you can't rearrange :smile:
Reply 15
lolhenry
Meaning you can't rearrange :smile:


You can, using the formula like above.
Reply 16
jasbirsingh
I know it's easier by putting in the number's first...But I need this equation for writing a program..So Please cany1 tell me how to re-arrange it because I have been trying to do but couldn't do it..


Do you HAVE to use this formula? Can't you just try another formula and work out an unknown from that, plug that unknown into a formula with T in it, then get T from that? That's what I do if I want to double check answers o.o
Reply 17
Depends on your question, in some:

ut is usually = 0
so rearrage from S=1/2at^2?
Reply 18
Use the quadratic formula. Don't bother rearranging it, use the formula for each individual question.
s=ut + 1/2at^2

s/t=u+1/2at

2s/t=u+at

2s/t-u=at

2s-u= at^2

2s-u/a= t^2

√(2s-u)/a= t

voila.