Converting Uncertainty in Millimeters to Meters for Radius Calculation

[rainstom07]

In a lab, i used a micro-caliper to measure the diameter of an indicator; I got 3.681 mm \pm 0.005 mm. However, i need the measurement to be in meters and i need to divide the measurement by 2 (as i need the radius, not diameter) for easy calculations. I know how to convert the 3.681 mm to meters, but what about the uncertainty?

radius of indicator:
3.681 mm * \frac{1 m}{1000 mm} * \frac{1}{2} = 0.00184\underline{0}5 m

uncertainty?:
\pm 0.005 mm * \frac{1 m}{1000 mm} * \frac{1}{2} = 0.00000\underline{2}5 m

Is this right?

Thanks in advance.

 

[mathman]

Yes. It is easier to understand if you think of the uncertainty in terms of percentage uncertainty. Then the units don't matter.