Hanging masses, beams and pivots: function and safe handling
Understand the hanger, beam and pivot roles, total suspended mass and why an equilibrium reading is not a safe load rating.
A hanging mass applies a force through its hanger. A beam transmits that force and its own weight to the supports. A pivot provides a turning reference. You need to know both the total load and where each force acts.
The trainer selects the beam, pivot, fittings and permitted loads. Use the moments practical for the full equilibrium investigation, not as a capacity test.
Account for the whole load
Include the hanger's mass and any assigned attachment that moves with it. Convert the complete mass to weight using the task's stated gravitational field strength; do not silently treat a mass label as a force label.
IOP's beam example relates balance to force and distance, while OpenStax's equilibrium explanation distinguishes the turning effects about a chosen pivot. For a horizontal beam with vertical loads, measure the arm to the load's line of action, not simply to an arbitrary edge of the hanger.
The beam's own weight may also contribute a moment. A pivot at its centre of gravity removes that contribution about the pivot; moving the pivot changes that moment.
Check the load limit even when the beam balances
Equal opposing moments can balance large loads. The supports and fittings must still withstand those loads. A level beam or equal calculated moments cannot tell you the maximum load the apparatus can safely hold.