Glossary
gear ratio
A gear ratio compares the teeth on two meshing gears. Divide driven teeth by driving teeth: the gear with more teeth turns slower and with more force.
A gear ratio compares the number of teeth on two meshing gears. Divide the teeth on the driven gear by the teeth on the driving gear: a 40-tooth gear driven by a 10-tooth gear turns four times slower and delivers about four times the turning force.
That exchange is the whole point of gearing. A larger driven gear trades speed for torque, which is how a car pulls away from rest; a smaller one trades torque for speed, which is how it cruises with the engine turning slowly. Reverse, neutral, and the difference between first gear and top gear are all ratios.
Questions usually give two tooth counts and ask which way the driven gear turns or how much slower it spins. Hold the rule: the gear with more teeth always turns more slowly and with more force, and gears in mesh turn in opposite directions to the one driving them.
Taught in
Related terms
- wheel and axle — A wheel and axle is a large wheel fixed to a smaller shaft so both turn together. Effort on the wheel gives a greater force at the axle.
- mechanical advantage — Mechanical advantage is how much a machine multiplies the force you apply: a lever, gear or pulley trades distance for force, so a small effort raises a large load.
Source: Official ASVAB — subtest descriptions (what each subtest asks) and the CAT-ASVAB scored-question counts (accessed 2026-09)