ASVAB Mechanical and Electrical Formulas: Levers to Ohm's Law

What the test expects you to bring

The official ASVAB program describes Mechanical Comprehension as knowledge of mechanical and physical principles, Electronics Information as knowledge of electricity and electronics, and General Science as knowledge of the physical and biological sciences. It also says you cannot use a calculator. The same rule covers Arithmetic Reasoning and Mathematics Knowledge, whose formulas are on the ASVAB math formulas page.

The clock is tight on Electronics Information. On the computer version it gives you 15 questions in 10 minutes, about 40 seconds each, while Mechanical Comprehension gives you 15 in 22 minutes. At 40 seconds an item, you have no time to rebuild a formula from first principles. The full timing table is on the ASVAB format page.

The examples below mix newtons and meters with pounds and feet, so practice in both. Use g = 9.8 m/s² for gravity, or 10 m/s² when a question says to.

Mechanical comprehension: the work rule behind every simple machine

Mechanical advantage is output force divided by input force. For an ideal, frictionless machine you can find it from distances instead: how far the effort moves divided by how far the load moves. That ideal figure is the IMA. The actual figure, load divided by the effort a real machine needs, is the AMA, and efficiency is AMA divided by IMA.

Efficiency example: the 10 ft ramp above has an IMA of 5. If friction means you actually need 125 lb to push the 500 lb load up it, the AMA is 500 ÷ 125 = 4, and the efficiency is 4 ÷ 5 = 80 percent.

A pulley item turns on one count. Count only the rope segments that hold up the moving block. Ignore the free end you pull on when it runs down from a fixed pulley, since that pulley only turns the direction of your pull. If the free end leaves the moving block and goes up to your hand, it counts.

Lever classes

The class depends on what sits in the middle. The mechanical advantage rule never changes: effort arm divided by load arm, with each arm measured from the fulcrum at a right angle to its force.

A wheelbarrow with its load centered 0.5 m from the wheel axle and its handles 1.5 m from the axle has an IMA of 3, so a 180 lb load takes 60 lb of lift at the handles.

Gears, belts and direction

Settle direction first, then speed. Across any mesh, teeth times rpm stays the same on both gears. For belts, diameter times rpm stays the same. Torque moves the other way: a gear that turns slower turns harder.

Torque, work, power and energy

Torque is force times the perpendicular distance from the pivot, and an object balances when the clockwise moments equal the counterclockwise moments. Work only counts force along the direction of motion. Holding a load still, or carrying it level, does no work on it in the physics sense.

Pressure and Pascal's principle

Pressure is force divided by area. Pascal's principle says pressure added to an enclosed liquid reaches every part of it undiminished, which is how a hydraulic jack multiplies force. Piston area grows with the square of the diameter, so a piston 3 times as wide has 9 times the area and 9 times the force.

Friction, springs and center of gravity

The Mechanical Comprehension guide has practice items on each of these setups.

Electronics information: Ohm's law and power

Voltage (V, in volts) is the push, current (I, in amperes) is the flow and resistance (R, in ohms) is the opposition. Navy training texts such as NEETS write voltage as E, so P = E × I is the same formula as P = V × I. Every resistor problem starts with V = I × R.

Series and parallel

Series parts share one current, and their voltage drops add up to the source. Parallel branches share one voltage, and their currents add up to the total. Total parallel resistance always comes out below the smallest branch.

The usual trap: resistors add in series, capacitors add in parallel. Two 6 µF capacitors in series give 3 µF, while two 6 Ω resistors in series give 12 Ω. Inductors follow the resistor rule.

Kirchhoff's rules in words

The junction rule: the current flowing into any junction equals the current flowing out of it. If 3 A enters and one branch carries 1 A, the other carries 2 A. The loop rule: around any closed loop, the voltage drops add up to the source voltage. With a 24 V battery and drops of 4 V and 8 V across two resistors, the third must drop 12 V.

Capacitance, inductance and AC

A capacitor stores charge and blocks steady DC once charged. An inductor is a coil that opposes changes in current and passes steady DC. A transformer changes AC voltage by its turns ratio and gives no output on steady DC.

Household power in the United States is 120 V rms at 60 Hz. It peaks near 170 V, because peak equals rms times about 1.414.

The resistor color code

Band 1 is the first digit, band 2 the second digit, band 3 the multiplier and band 4 the tolerance. The order from 0 to 9 is black, brown, red, orange, yellow, green, blue, violet, gray, white, which the NEETS Module 1 memory aid "Bad Boys Run Over Yellow Gardenias Behind Victory Garden Walls" keeps straight. Gold and silver mean one thing as a third band and another as a fourth, and brown and red can also sit in the tolerance position.

Yellow, violet, red, gold reads 4 and 7 times 100, so 4,700 Ω or 4.7 kΩ, plus or minus 5 percent. That allows anything from 4,465 to 4,935 Ω. Brown, black, orange is 10 times 1,000, or 10 kΩ.

Metric prefixes

Volts divided by kilohms gives milliamps, which skips the zeros: a 9 V source across 3 kΩ drives 3 mA. The Electronics Information guide covers the symbols, meters and fault-finding items that sit beside these formulas.

General science physics that overlaps

The official description of General Science, knowledge of the physical and biological sciences, overlaps the "mechanical and physical principles" of Mechanical Comprehension. Newton's laws, density and specific gravity fall under both descriptions, so learning them once serves 2 subtests.

The General Science guide covers the biology, chemistry and earth science that fill the rest of that subtest, and the technical subtests overview shows which Service composites use Mechanical Comprehension and Electronics Information.

Sources

• Official ASVAB program website, Applicants section, "What to Expect" page (subtest content descriptions for General Science, Electronics Information and Mechanical Comprehension, and the no-calculator rule) and the applicant FAQ on calculators, accessed October 2026.
• OpenStax, College Physics 2e (Rice University, 2022): sections 4.2 to 4.4 (Newton's laws); 5.1 Friction; 7.1 Work; 7.2 Kinetic Energy; 7.3 Gravitational Potential Energy; 7.7 Power; 6.1 Rotation Angle and Angular Velocity (v = rω: a belt that does not slip moves both pulley rims at the same speed, the basis of the belt speed rule); 9.2 The Second Condition for Equilibrium (torque); 9.3 Stability; 9.5 Simple Machines; 11.2 Density (Table 11.1, ice 0.917 g/cm³); 11.3 Pressure; 11.4 Variation of Pressure with Depth; 11.5 Pascal's Principle; 11.7 Archimedes' Principle (specific gravity); 16.1 Hooke's Law; 19.5 Capacitors and Dielectrics; 19.6 Capacitors in Series and Parallel; 20.2 Ohm's Law; 20.4 Electric Power and Energy; 20.5 Alternating Current versus Direct Current (120 V rms, 170 V peak); 21.1 Resistors in Series and Parallel; 21.3 Kirchhoff's Rules; 23.7 Transformers; 23.9 Inductance; 23.11 Reactance, Inductive and Capacitive.
• Naval Education and Training Professional Development and Technology Center, Basic Machines, NAVEDTRA 14037: chapter 1 Levers (lever classes and examples), 2 Block and Tackle, 3 The Wheel and Axle, 4 The Inclined Plane and the Wedge, 5 The Screw (2πr ÷ pitch), 6 Gears (idler gears, speed and mechanical advantage of gear trains; belts can creep or slip, gears cannot), 7 Work (efficiency) and 10 Hydrostatic and Hydraulic Machines (Pascal's principle).
• Naval Education and Training Professional Development and Technology Center, Navy Electricity and Electronics Training Series (NEETS) Module 1, Introduction to Matter, Energy, and Direct Current, NAVEDTRA 14173, September 1998: chapter 1, Table 1-1, Standard Color Code for Resistors and the tolerance band; chapter 1, the memory aid for the color order; chapter 3, power formulas, 1 horsepower = 746 watts, and Kirchhoff's voltage and current laws.
• Naval Education and Training Professional Development and Technology Center, NEETS Module 2, Introduction to Alternating Current and Transformers, NAVEDTRA 14174, September 1998: chapter 2, Series Inductors Without Magnetic Coupling (page 2-17) and Parallel Inductors Without Coupling (page 2-19).
• National Institute of Standards and Technology, Office of Weights and Measures, "Metric (SI) Prefixes" reference table.