I used a ruler and found the uncertainty to be +/- 0.05cm. If I used the ruler twice when measuring, should I just multiply the original uncertainty by 2, or how does it work?

Question

irishboy123 · Answer

best case is you luck out and are out by $+ 0.05$ then $- 0.05$ , or $- 0.05$ then $+ 0.05$ , as the errors cancel, but you are trying to cancel the the theoretical uncertainty, ie huch MIGHT you be out -  so you need to look at worst case:

       ie you could be out by $+ 0.05$ both times;  or $- 0.05$ both times

so you are certain to within which overall tolerance?

alphabeta · Answer

Ok, so if I understand you right, my new uncertainty (if we look at the worst case scenario) would be +/- 0.1?

irishboy123 · Answer

$$\checkmark$$

alphabeta · Answer

Woho, thanks for your help!