PHY.1:2 - Problem

A physically different experiment can resemble the original while answering a different question. Keeping shape preserves length ratios. It can still change the competition between weight and strength, inertia and friction, propagation and absorption, or reaction and transport. An experiment that preserves a final value can also change the path by which that value is reached.

The difficulty is constructing the conditions of a useful comparison. A familiar dimensionless number can help, but selecting it requires knowing which physical effects it compares. Several relevant conditions can demand incompatible changes to the same material or control. The requested result determines whether that conflict must be removed or whether a more limited comparison will suffice.