ASVAB Mechanical Comprehension

Energy

The ability to do work, which comes in several different forms.

Kinetic Energy

Energy present in a moving object.

Potential Energy

Stored energy that can be released under certain conditions (e.g., an object lifted off the ground).

Chemical Energy

Energy stored in chemicals (like a battery) that remains potential until released by a chemical reaction.

Electric Energy

Energy created by moving electrons in an electric current.

Nuclear Energy

Energy released by reactions within the nucleus of an atom.

Force

A push or pull on an object that has both magnitude (strength) and direction.

Gravity

An attractive force between objects that pulls everything on Earth toward its center, causing falling objects to accelerate.

Acceleration

The change in velocity (speed in a particular direction) over time.

Friction

A force resulting from two surfaces touching that acts as resistance against the movement of an object.

Compression

A force that pushes two or more materials together (e.g., air or water pressure).

Tension

A force that pulls materials apart.

Machines

Devices that multiply force or motion, ranging from simple single-force tools to complex compound combinations.

Mechanical Advantage (MA)

The factor by which a machine multiplies input force, calculated as Load / Effort or Effort Distance / Load Distance.

Work

A specific force applied over a specific distance.

Simple Machines

Basic devices used to multiply a single force, including the lever, pulley, inclined plane, gear, wedge, wheel and axle, and screw.

Fulcrum

The stationary pivot point around which a lever rotates.

Load (Lever)

The object or weight to be lifted or squeezed by a lever.

Load Arm

The distance on a lever from the load to the fulcrum.

Effort (Lever)

The input force applied to a lever to move or squeeze the load.

Effort Arm

The distance on a lever from the point of applied effort to the fulcrum.

Class 1 Lever

A lever with the fulcrum located between the load and effort (e.g., seesaw, crowbar, balance scale).

Class 2 Lever

A lever with the load positioned between the effort and fulcrum (e.g., wheelbarrow); effort distance is always greater than load distance.

Class 3 Lever

A lever with the effort applied between the load and fulcrum (e.g., hammer driving a nail, human forearm); effort distance is shorter than load distance.

Pulley (Block and Tackle)

A simple machine using ropes and grooved wheels where MA equals effort distance divided by load distance, or the number of shortening supporting strands.

Gear Mechanical Advantage Formula

MA = Number of teeth on Driven gear / Number of teeth on Driving gear.

Sheave System Mechanical Advantage Formula

MA = Driven sheave diameter / Drive sheave diameter.

Inclined Plane

A ramp used to lift heavy objects; MA is calculated as horizontal length divided by vertical rise.

Wedge

A portable inclined plane where MA equals effort distance divided by load distance.

Wheel and Axle

A simple machine formed by a fixed wheel and axle rotating together; MA equals wheel radius (effort distance) divided by axle radius (load distance).

Compound Machine

A combination of two or more simple machines working together; total MA is found by multiplying the individual MAs together.

Structural Load Principle

When a load is centered between two supports, weight is split equally; if off-center, the support closer to the load bears more weight.

Fluid

Any substance that flows and takes the shape of its container, including both gases and liquids.

Atmospheric Pressure at Sea Level

Standard air pressure equal to 14.7 pounds per square inch (lb/in²).

Pneumatic Systems

Mechanical systems that perform work using compressed air or gas.

Behavior of Gas Under Compression

When compressed, gas warms up (gains thermal energy) and accumulates potential energy.

Behavior of Gas Under Expansion

When a gas expands, its internal pressure drops and its temperature cools down.

Behavior of Gas Under Cooling

When a gas cools without a change in surrounding pressure, its volume decreases.

Water Incompressibility Principle

Because water cannot be compressed, total volumetric flow rate through a pipe system remains constant everywhere.

Bernoulli's Principle (Fluid Speed and Pressure)

When a liquid speeds up, its pressure drops; when it slows down, its pressure increases.

Water Depth Pressure Principle

Pressure at the bottom of a water container increases with depth and equals total water weight divided by base area.

Net Gain Rate Formula for Tanks

Net Gain Rate = Inflow Rate − Outflow Rate (ensuring both rates share the same time units before calculating).

Work

a specific force applied over a specific distance. For example, your arm does work when it

uses force to lift a heavy object. Thusly a lever does also work when it uses force to lift an object.