EIAT mechanical aptitude: levers, pulleys, gears and hydraulics

Mechanical aptitude (often called mechanical comprehension) is 35 of the EIAT's 100 questions, according to NEIEP's study guide. If you have not studied physics it can sound intimidating. NEIEP's own examples, though, ask you to judge what happens in a diagram rather than calculate a number, and a handful of ideas covers most of them.

What NEIEP says it covers

The official study guide is specific. It names basic mechanics (levers, pulleys and gears), hydraulics (area and pressure), and fulcrums and levers, meaning how objects of different weights can be balanced. Those are the topics to prepare.

The question shape

This is worth understanding before you practice. NEIEP's four example questions are all judged from a diagram: which way a rod turns, which rope moves a box faster, which ladder is more likely to stay up, and which way a rod travels when a pulley turns. Each offers two candidate answers and a third such as "no difference" or "either".

So in those examples you are not producing a number; you are looking at a picture and deciding which of two things happens. Practice built only around four-option calculations prepares you for something different.

The rules that answer most of them

Gears

Two meshed gears turn in opposite directions. Along a row, the direction flips at every gear, so the first and third turn the same way. The gear with fewer teeth turns faster. Tooth counts change speed, never direction.

Levers and fulcrums

Turning effect is weight multiplied by distance from the pivot. A light weight far out balances a heavy one close in. The same rule explains why pushing at the far end of a bar takes less force than pushing near the pivot.

Pulleys

Count the rope sections actually supporting the load. Two sections halve the effort, three thirds it. A single fixed pulley supports the load on one section, so it changes the direction of your pull but gives you no advantage. Whatever you gain in force you pay for in rope.

Hydraulics

Pressure is the same throughout the fluid, and force equals pressure times area. The wider piston pushes harder and moves less far. That is a bottle jack.

Stability and friction

An object tips when its center of weight passes outside its base, so a wide, low object is hard to tip. A ladder pushes outwards harder the further its foot is from the wall, so the more upright one is less likely to slip.

Nothing comes for nothing

If one idea ties the section together, it is that no arrangement gives you something for free. Less force always means more distance. A long ramp, a block and tackle, a long wrench — all the same trade. When a question asks what the catch is, that is the catch.

How to practice

Work from diagrams, not from formulas. Our mechanical comprehension practice draws every question, in the comparison format the real paper uses, and explains the reasoning rather than the arithmetic. For deeper refreshers, see gears, levers, pulleys and hydraulics.