EIAT mechanical comprehension guide: levers, pulleys, gears and hydraulics

Mechanical comprehension is 35 of the 100 EIAT questions. If you have not studied physics it can sound intimidating. In practice it rests on about six ideas, and you are almost never asked to calculate anything.

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What NEIEP says it covers

The official study guide is unusually specific. It names basic mechanics — levers, pulleys and gears — along with hydraulics, meaning area and pressure, and fulcrums and levers, meaning how objects of different weights balance. That is the whole syllabus.

The question shape

This is the part worth understanding before you practise. NEIEP's example questions are all comparisons judged from a diagram: which way does the rod travel, which rope moves the box faster, which ladder is more likely to stay up. They offer two candidate answers and usually a third along the lines of "no difference".

So you are not being asked to produce a number. You are being asked to look at a picture and say which of two things happens. Practice material built around four-option calculations is preparing you for a different test.

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 centre 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 spanner — all the same trade. When a question asks what the catch is, that is the catch.

How to practise

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.