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Mechanical Comprehension

Mechanical Comprehension tests your understanding of physical and mechanical principles, including forces, simple machines, and the properties of materials. Questions often show a situation and ask how objects will move or how much force is needed. This subtest is not part of the AFQT but counts toward mechanical and technical job qualifications. Understanding simple machines and basic physics is the foundation for success.

Forces and Motion

Forces push and pull on objects and determine whether they move. Balanced and unbalanced forces produce different results.

Balanced forces

Equal and opposite forces cancel out, so an object stays still or keeps a constant motion.

Unbalanced forces

A net force in one direction causes an object to accelerate that way.

Friction opposes motion

Friction acts between surfaces sliding against each other and resists their movement.

Gravity acts downward

Gravity pulls objects toward Earth's center and gives them weight.

Simple Machines

Simple machines make work easier by changing the size or direction of a force. The six classic types appear throughout this subtest.

Levers multiply force

A lever pivots on a fulcrum to increase the force applied to a load.

Wheel and axle

A doorknob or steering wheel turns a small axle with a larger wheel for more turning force.

Pulleys change direction

A fixed pulley lets you pull down to lift a load up, and added pulleys reduce effort.

Inclined planes and wedges

A ramp is an inclined plane, and a wedge is a moving inclined plane that splits objects.

Mechanical Advantage and Gears

Mechanical advantage measures how much a machine multiplies force. Gears transfer motion and change speed and direction.

Increase mechanical advantage

A longer effort arm on a lever multiplies force more, easing the lifting of heavy loads.

Gear direction

Two meshed gears turn in opposite directions.

Gear speed trade-off

A small gear driving a large gear turns the large one more slowly but with more torque.

Fulcrum placement

Placing the fulcrum closer to the load increases a lever's mechanical advantage.

Energy, Springs, and Fluids

Mechanical systems store and transfer energy, and fluids exert pressure. These principles round out the subtest.

Gravitational potential energy

An object stores more potential energy the higher it is raised.

Elastic potential energy

A compressed or stretched spring stores energy that becomes motion when released.

Air pressure and altitude

Air pressure is greatest at sea level and decreases with altitude.

Energy conservation

Energy is not lost but changes form, such as potential energy converting to kinetic energy.

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Last updated: July 2026