cancel
Showing results for
Did you mean:
cancel
Showing results for
Did you mean:

7-Bedrock

## UNITS & EXPONENTIATION

Has anyone come up with a simple approach to handling values with units that are then used in an expression that has exponents on the values.  For example, I know there has been previous discussion of concrete compressive strength, f"c being used in an expression where the square root of f'c is used.  The solution seems to be to divide out the units under the radical.

In the case of a fractional exponent, i.e., (12 in) ^1.5, I am dividing the value by the units (inches in this case) and the result is acceptable.

Thank you for your input and suggestions.  Perhaps the people at PTC can issue an instruction paper on handling units and exponentiation.

1 ACCEPTED SOLUTION

Accepted Solutions
23-Emerald II
(To:wbell)

@wbell wrote:

Has anyone come up with a simple approach to handling values with units that are then used in an expression that has exponents on the values.  For example, I know there has been previous discussion of concrete compressive strength, f"c being used in an expression where the square root of f'c is used.  The solution seems to be to divide out the units under the radical.

In the case of a fractional exponent, i.e., (12 in) ^1.5, I am dividing the value by the units (inches in this case) and the result is acceptable.

Thank you for your input and suggestions.  Perhaps the people at PTC can issue an instruction paper on handling units and exponentiation.

I believe that the "official" method of handling units in non-linear expressions is to use the SIUnitsOf function (bearing in mind that Mathcad internally converts all units to SI units, which is why dividing by the actual units usually works).

See:

Stuart

(At the entirely justifiable risk of seeming like a crank, there is some mathematical justification for believing that there actually isn't a problem with using units with non-linear expressions, provided one understands the underlying physics.   Nor is there a good reason why angles should not be regarded as a base quantity rather than as a dimensionless quantity)

23-Emerald II
(To:wbell)

@wbell wrote:

Has anyone come up with a simple approach to handling values with units that are then used in an expression that has exponents on the values.  For example, I know there has been previous discussion of concrete compressive strength, f"c being used in an expression where the square root of f'c is used.  The solution seems to be to divide out the units under the radical.

In the case of a fractional exponent, i.e., (12 in) ^1.5, I am dividing the value by the units (inches in this case) and the result is acceptable.

Thank you for your input and suggestions.  Perhaps the people at PTC can issue an instruction paper on handling units and exponentiation.

I believe that the "official" method of handling units in non-linear expressions is to use the SIUnitsOf function (bearing in mind that Mathcad internally converts all units to SI units, which is why dividing by the actual units usually works).

See: