Structures with multi-force members solved by dismantling into free bodies.
Frames and machines contain multi-force members, so members are dismantled and each free body analysed with pin forces as equal and opposite pairs. Pliers, cranes and excavators are machines.
A pair of pliers multiplies grip force through lever geometry.
Frames and machines contain multi-force members that cannot be treated as simple two-force members, so they need a different approach.
Structures with multi-force members solved by dismantling into free bodies.
Frames and machines contain multi-force members that cannot be treated as simple two-force members, so they need a different approach.
A frame has members that carry bending and can support loads between joints. A truss only carries axial forces at joints.
Take the whole structure as a free body to find the external reactions, then dismantle it into individual members and draw each free body.
Typical applications include analysing a hand-operated press where a lever transmits force to a jaw, finding the forces at pins in a crane frame and solving a clamp mechanism with several connected members.
Study "Distributed loads" first (topic 16 of 106 in Engineering Mechanics). It covers the groundwork this topic builds on.
Identify two-force members first. Apply Newton's third law at pins. Solve the whole structure for reactions first.
A pair of pliers multiplies grip force through lever geometry.
The next topic is "Cables and arches", which builds directly on this one.
It is classed as Beginner in Engineering Mechanics (topic 17 of 106). It is an entry-level topic. It relies only on basic school mathematics and the ideas introduced earlier in this discipline.
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