MathCAD Units Help

Forum|Forum|13 years ago
March 4, 2013
3 replies
30498 views

I am using MathCAD Prime 2.0 for design calculations for a building I am engineering. I am fairly new to MathCAD, only learning a little about it in college. However, I am running into a units issue when calculating pounds per linear foot (lb/ft) to just pounds (a point load). I am taking 480 PLF * 4 ft, the feet should cancel out and you are left with just pounds. MathCAD is spitting out a lb*f, like the units for a moment. When I go to change the units to just pounds then it changes my units to (ft/s^2)*lb? Please explain to me what is going wrong here. See below for a screen shot:

Please note that the answer is correct, 1920 pounds is the right answer. Just the wrong units.

Thank you in advance,

Jon Recknagel | Structural Designer

Other

Best answer by ptc-4992678

I just answered my own question. A "lbf"= a pound force. It seems like they could have just left it at "lb" we are all aware that pounds is a force. Just my opinon I guess. Thanks anyway.

P

ptc-4992678

AuthorAnswer

1-Visitor

I just answered my own question. A "lbf"= a pound force. It seems like they could have just left it at "lb" we are all aware that pounds is a force. Just my opinon I guess. Thanks anyway.

R

RichardJ

19-Tanzanite

It seems like they could have just left it at "lb" we are all aware that pounds is a force.

The pound is a unit of mass, not force.

P

ptc-4992678

Author

1-Visitor

m=F/G, most engineering firms (in the US anyway) do not work in terms of metric units of mass. Everything is in pounds, a force. When you step on the scale at home you do not read your weight in terms of mass, you read your weight it terms of pounds, due to gravity, which is a force.

B

BillWadsworth

10-Marble

The "lbf", pounds force is there to differentiate between pounds mass, which is just "lb". Something which matters greatly when doing dynamics, rather than statics.