# MERM Sample Exam No. 9 - Dimensional Analysis error?



## abourne (Oct 20, 2010)

MERM Sample exam No. 9, solution states:

1 Centistoke = 0.216 SUS

So, if

Kinematic Viscosity (KV) = 110 Centistokes

The solution has:

KV = [110 Centistokes] x [1 Centistoke / 0.216 SUS] = 509 SUS

Is this error with dimensional analysis?

In order for "Centistokes" to CANCEL OUT, shouldn't it be as follows:

KV = [110 Centistokes] x [0.216 SUS / 1 Centistoke] = SUS

Hence, equating to 110 x 0.216 = 23.76 SUS

Does the solution have an error?

Or is there something I'm not seeing here?


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## abourne (Oct 21, 2010)

Response:

The result shown in the ME Sample Exam is correct, but is written incorrectly. It should be written as

viscosity = (110 cSt)/(0.216 cSt/SUS) = 509 SUS

MERM12 does not tell the whole story about viscosity unit conversions, and offers some approximate relationships on pg. 14-6.


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