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Chemistry Forums for Students => Physical Chemistry Forum => Topic started by: Mikez on May 18, 2006, 10:52:00 PM

Title: Quick Unit Converison Problem
Post by: Mikez on May 18, 2006, 10:52:00 PM

how do I convert between m/s to k/h?

and

how does significant digits work? (my teacher is telling me that 1.000 has 4 significant digits???)

thanks

Title: Re: Quick Unit Converison Problem
Post by: mike on May 18, 2006, 11:17:56 PM

1000 metres in 1 km

60 seconds in 1 minute and 60 minutes in 1 hour

Significant digits:

All non-zero digits are significant: 1234 has four sig. fig.
zeros before a digit are not significant: 0.00054 has two sig. fig. (5 and 4)
zeros between digits are significant: 4008 has 4 sig. fig.
zeros after a digit and behind a decimal point are significant: 7.40500 has six sig. fig. (so your teacher is correct 1.000 has four sig. fig.)
zeros afte a digit but not behind a decimal point are generally not significant (but this is not always the case, and this is why scientific notation is prefered) for example: 96000 is ambigous which digits are significant (I would say definitely two, ie 9 and 6) so using scientific notation you can show which are significant: 9.6 x 10⁴ (2 sig. fig.) or 9.60 x 10⁴ (3 sig fig) etc etc

Title: Re: Quick Unit Converison Problem
Post by: billnotgatez on May 19, 2006, 03:41:57 AM

1 meter    60 seconds   60 minutes      1 kilometer   3.6 kilometers 
-------- * ---------- * ---------- * -------------- = --------------- 
1 second    1 minute     1 hour      1000 meters         1 hour       

Title: Re: Quick Unit Converison Problem
Post by: Borek on May 19, 2006, 03:58:37 AM

60*60/1000 = ???

Thing is, I just happened to remember what the conversion factor is ;)

Title: Re: Quick Unit Converison Problem
Post by: billnotgatez on May 19, 2006, 04:15:49 AM

The way I depicted it shows how the units of measurement cancel out. Admittedly that is probably not the short hand or quick method.

Title: Re: Quick Unit Converison Problem
Post by: Borek on May 19, 2006, 04:20:48 AM

Quote from: billnotgatez on May 19, 2006, 04:15:49 AM

The way I depicted it shows how the units of measurement cancel out. Admittedly that is probably not the short hand or quick method.

Units are OK, just your math is wrong.

Title: Re: Quick Unit Converison Problem
Post by: billnotgatez on May 19, 2006, 05:08:12 AM

I edited it – those pesky decimal places - thanks

Title: Re: Quick Unit Converison Problem
Post by: Unsichtbar on May 20, 2006, 03:33:54 PM

Quote from: Mikez on May 18, 2006, 10:52:00 PM

how do I convert between m/s to k/h?

m/s to km/h: x3.6
km/s to m/s: ÷3.6

Quote from: Mikez on May 18, 2006, 10:52:00 PM

how does significant digits work? (my teacher is telling me that 1.000 has 4 significant digits???)

Significant digits are the number of digits without the "dot" (or "comma")... (I think that's)