Glossary
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.
A wheel and axle is a large wheel fastened to a smaller shaft so that both turn together. Apply the effort to the wheel and the axle does the work with more force, because your effort travels around a much larger circle than the load does.
The mechanical advantage is set by the two radii: divide the radius of the wheel by the radius of the axle. A handle 30 cm from the center turning a shaft 3 cm across multiplies your force about ten times. That is why a screwdriver handle, a doorknob, a steering wheel, a windlass and a tap handle are all the same machine wearing different clothes.
Turned the other way the same device costs force and gains speed, as when you rotate the axle to spin the wheel fast. Like every simple machine it trades a smaller force over a longer distance for a larger force over a shorter one.
Taught in
Related terms
- pulley — A pulley is a wheel with a grooved rim that carries a rope. A fixed pulley changes the direction of the pull; a movable pulley or block and tackle reduces the force needed.
- 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.
Source: Official ASVAB — subtest descriptions (what each subtest asks) and the CAT-ASVAB scored-question counts (accessed 2026-09)