Mechanical Reasoning
What the section tests
Mechanical reasoning questions check whether you can reason about how physical systems behave, not whether you have memorized formulas. Expect questions on levers and torque, pulleys and gear trains, simple machines, pressure and fluid behavior, basic electrical circuits, and the relationship between force, work, and motion. Most items present a described setup in words and ask which way something moves, which side is heavier, or how speed and force trade off.
Concepts to master
Understand that torque depends on force times distance from the pivot, so a small force far from the pivot can balance a large force close to it. Know that a single fixed pulley changes direction but not effort, while movable pulleys trade distance for force. For gears and belt drives, a larger wheel turns slower and with more torque than a smaller one meshing with it; direction reverses between meshing gears but stays the same on a crossed or open belt depending on routing. In fluids, pressure increases with depth and is transmitted equally in a closed system. In series circuits, current is the same everywhere and voltage divides; in parallel, voltage is the same and current divides.
Traps to watch
Questions often describe a system that looks balanced but is not, or ask about speed when the answer hinges on torque. Read whether a pulley is fixed or movable, whether gears mesh directly or are linked by a belt, and whether a circuit is series or parallel. Distinguish mass from weight and effort from load.
Worked example
A lever has its pivot at one end, a 60 lb load 2 ft from the pivot, and effort applied 6 ft from the pivot. Balance requires effort × 6 = 60 × 2, so effort = 20 lb. Rule of thumb: multiply force by distance on each side; the side with the larger product wins.