Is the Answer in Meters per Second or Millimeters per Second?

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SUMMARY

The discussion centers on the conversion of units in fluid dynamics, specifically whether to express velocity in meters per second (m/s) or millimeters per second (mm/s). The continuity equation A1*v1=A2*v2 is applied, with an example involving a radius of 10.0 mm and a velocity of 0.200 m/s. Participants confirm that converting all measurements to meters is essential for accuracy, and that the final answer can be converted back to millimeters if needed. The importance of significant figures in calculations is also emphasized.

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  • Study the application of the continuity equation in various fluid dynamics scenarios
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Units -- is this m/s or mm/s?

Homework Statement


N/A

Homework Equations


Continuity
A1*v1=A2*v2

A=pi*r²

The Attempt at a Solution



I've solved a problem as follows

(pi * 10.0mm²)(0.200m/s)=(pi * 2.50mm²)(v2)
3.20 xx/s = v2

I am pretty sure it's in m/s, but having the radii in millimeters is confusing me. I would convert all to meters, but I am required to solve using 3sf, so I would lose accuracy on the 2.50mm.

Am I correct in thinking the answer is in m/s?
 
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You can never lose accuracy by converting millimeters to meters, and vice-versa, since the two are separated by a constant. You have the right idea - turn everything into meters, and if you want, you can turn the end product back into millimeters.
 


Heh, I converted 2.50mm to 0.025m and, for whatever reason, I got the idea in my head that I would have to reduce it to 0.020m to still have 3sf. I went back and did a bit of review on sf and figured it out :p

Thanks for the response!
 

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