PHY.2:4.1 - Choose what the source must help you obtain

State the target question in the terms of the work. You might need a response to an input, a possible mechanism for an observed change, a limit on a proposed behavior, or an arrangement that lets you manipulate an otherwise inaccessible relation. Say what is already known and what remains proposed about the target.

Follow the intended consequence to the relevant participants and interactions. A force on one body may change another through a stored deformation; a change at a boundary may propagate through transport. Recover the target relation that the source must help explain or use. B.5.FM and B.5.TU support this first account and its relation to a theory.

Keep the first construction as small as that question permits. For a question about coupling, two interacting parts can expose what a whole-device sketch leaves implicit. If the target mechanism is unknown, begin with an observed dependence and a proposed way it could arise. The proposal gives something to develop even before a complete target theory is available.