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Simple question with SUVAT equations.

Hi there.

I'm taking AS Physics this year and just having a bit of trouble with some parts of this homework we've been set, I'd be grateful if omeone could help.

"An object in Free Fall has a constant acceleration of 9.81 ms-2. It goes past 2 light gates. The time interval between passing the first and the second is 0.269s. The distance between is 1.36m.
1) What is the object's speed as it passes the first light gate?
2) At what height from the first light gate was it dropped?"

I was kind of completely lost with this, but I tried this:

S = 1.36 m
T = 0.269 s
A = 9.81 ms-2
U = speed at first light gate

So s = ut + 1/2at^2;
1.36 = u * 0.269 + 9.81 * 0.269^2

Moving u over leves s/t:

u = 1.36/0.269 + (9.81 * 0.269^2)/2
u = 2.88 ms-1 (3sf)

But the textbook gives the answer as 3.74 ms-1?
I suspect it's something to do with my atrocious re-arranging skills...
Reply 1
Avatar for DeanK2
DeanK2
Forget this post

EDIT: completely misread quaetion
Reply 2
Avatar for beesbees
beesbees
OP
14
:o:

Thanks, I've been looking at this for like 20 minutes now and it finally just clicked!
Reply 3
Avatar for Jkoo22
Jkoo22
13
How did you move the s and ut round which made neg half from stage1 to stage 2?

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