How Do You Calculate Speed and Uncertainty with Given Measurements?

[Alipepsi]

Homework Statement

Hey there, I need some help with uncertainties and how to find the speed of a moving object. I have tried to solve the problem several times but my answer seems to be wrong.

Formula for speed : v=d/t
My uncertainties: 0.5cm (distance) and 0.5s for time. The uncertainties were measured with the same analog.
I did the experiment 15 times and got different speed result of the object each time. The total sum of the speeds ( 15 trials) was 44.99s. The average of that is 2.99 (15/44.99)
Oh and my measuring device was 228cm long (exact)

I need to find out the speed and the uncertainties
If I missed any detail please please let me know
PLEASE HELP! I'am very frustrated right now..=S

Homework Equations

Formula to use : v=d/t

The Attempt at a Solution

v=d/t
= (228 +\- 0.5)m/(2.99+\- 0.5)s
228 divided by 0.5 = 456%
2.99 divided by 0.5= 5.78%
456% +5.78%=461.98%

so now 461.98% * 76.2 ( which I got by diving 288 and 2.99)
my final answer was v=76.25m? +\- 39%..
I'am confused..

 

[Alipepsi]

Actually spend hours on trying to solve this :S
Help will be greatly appreciated!

 

[Alipepsi]

anyone?

 

[ojs]

Check out this site here: http://www.rit.edu/cos/uphysics/uncertainties/Uncertaintiespart2.html

 

[Alipepsi]

Okey, thanks