Units in Mathcad
Units in Mathcad
Units in Mathcad
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<strong>Units</strong>_<strong>in</strong>_MC.xmcd9/25/2007Us<strong>in</strong>g <strong>Units</strong> (SI)<strong>Units</strong> of Pressure - Pascal (Pa), Pounds per square <strong>in</strong>ch (psi) which is reallylb-force per square <strong>in</strong>ch1 lbf = 6.895 × 10 3 Pa 6895Pa = 1⋅psi<strong>in</strong> 21 lbf<strong>in</strong> 2= 1⋅psi1psi = 6.895 10 3× Pa1psi⋅1<strong>in</strong> 2Now, multiply<strong>in</strong>g psi * <strong>in</strong>^2 yields a force:= 4.448 NRemember, there is a difference between lb (pound-mass) andlbf (pound force)So:4.448N = 1⋅lbf(substitute lbf for units)if you use lb, then you get strange results such as:4.448N = 9.806 m ⋅lbs 2You might recognize the 9.806 m/sec^2 as the acceleration of gravity.Unfortunately, if this was used <strong>in</strong> a complex function, you would have noidea why you had strange values and units. The lb is pound-mass as faras <strong>Mathcad</strong> is concerned.
To set the units for an entire system, use Tools - Worksheet Options<strong>Units</strong>_<strong>in</strong>_MC.xmcd9/25/2007
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