A question about signifigant digits

[doctordiddy]

Hi, I was just wondering if there was a rule in signifigant digits that says an extra digit is added if the full answer happens to be very far from the signifigant digit answer?

I know it sounds confusing but what I mean is this

I solved a question using these numbers

vi=0
a=9.8 m/s^2
t= 2.6s

I was looking for final velocity, and I found that the answer before signifigant digits is 25.48m/s, so I thought the answer after signifigant digits would be 25 m/s, but instead it was 25.5 m/s. Can anyone tell me why this is?

 

[ehild]

This is the case where an extra digit is added. :)

ehild

 

[doctordiddy]

This is the case where an extra digit is added. :)

ehild

So how close exactly does it have to be?

For another question my units were

vi=0
vf=65
a=3

but the d i got was 704, when I thought it should have been 700

 

[Tide]

It looks to me like this was from a textbook problem and I surmise that either the author(s) of the text or your instructor simply didn't follow the rules for significant digits. Given the information you provided, your answer is correct.

 

[doctordiddy]

It looks to me like this was from a textbook problem and I surmise that either the author(s) of the text or your instructor simply didn't follow the rules for significant digits. Given the information you provided, your answer is correct.

Yeah after doing more questions from the same website I found that out, this is the website I got it from, it seems like all the answers are rounded to 3 decimal places if they have more than that.

http://www.physicsclassroom.com/class/1dkin/u1l6d.cfm#q3