This page is devoted to frequently asked questions (FAQ) related to units.
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In which unit is mass entered?
Answer: Mass must be given in consistent mass units (W/g). Force, length, and temperature are primary units. Mass is then derived from these units secondarily. Accordingly, notable points include the following:
- Ton represents ton-force (tonf) when the Ton, m, C unit set is chosen.
- A mass of 1.0 tonm, also known as a tonne or metric ton, is given as 1000 kg. In a standard gravity field, the weight of 1.0 tonm produces 1.0 tonf, or a ton-force, given as 9810 Newtons (N).
- Because mass must be entered in consistent units (W/g), and not as a force, 1.0 tonf would be entered as W/g = 1 tonf / (9.81 m/s2) = 0.102 tonf * s2/m.
Additional information may be found in the Mass units article and in the
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CSI
Analysis Reference Manual (Joints and Degrees of Freedom > Masses, page 39).
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Related Incident:
- Unknown macro: {incident}The following explanation is provided in Incident 30267: In SAP2000, the basic units are Force (lb, kip, N, kN, etc.), Length (ft, in, m, mm, etc.), Time (second), and Temperature (F, C). Mass is a derived unit and SAP2000 does not use lb or kip for mass units, they are only used for force units. Weight has units of F, where F is force. CONSISTENT mass units are given by F/(L/T^2), where L is length, T is time, and the mass units are simply force divided by UNIT acceleration.