AFOQT Physical Science: Everything You Need to Know (PhD-Level Breakdown)

The AFOQT Physical Science subtest is 20 questions in 10 minutes. It covers mechanics, thermodynamics, electricity and magnetism, waves and optics, and nuclear basics. As a PhD nuclear engineer, this is the subtest I look forward to helping students with most — because the physics is real, the concepts connect to each other, and with the right conceptual foundation, every question becomes approachable.

This guide gives you a complete content review organized by topic, with formula tables and the conceptual understanding you need to reason through questions you have never seen before.

Section 1: Mechanics

Mechanics covers forces, motion, and energy. These questions form the largest share of the Physical Science subtest and connect directly to the physics underlying flight.

Newton's Laws and Force

Newton's three laws are foundational. First law: an object at rest stays at rest and an object in motion stays in motion unless acted on by a net external force (inertia). Second law: F = ma. Third law: every action has an equal and opposite reaction.

The second law is the workhorse. If a question tells you force and mass, you can find acceleration. If it tells you force and acceleration, you can find mass. Keep units straight: force in Newtons (N = kg·m/s²), mass in kilograms, acceleration in m/s².

Kinematics

Quantity	Formula	Variables
Velocity (constant accel.)	v = v₀ + at	v₀ = initial velocity, a = acceleration, t = time
Displacement	x = v₀t + ½at²	x = displacement
Velocity-displacement	v² = v₀² + 2ax	Useful when no time given
Free fall acceleration	g = 9.8 m/s²	Near Earth's surface

Momentum and Impulse

Momentum (p) = mass × velocity (p = mv). Impulse = force × time = change in momentum. Conservation of momentum: in a closed system with no external forces, total momentum before equals total momentum after. This shows up in collision problems.

Energy and Work

Concept	Formula
Work	W = F × d × cos(θ)
Kinetic energy	KE = ½mv²
Gravitational potential energy	PE = mgh
Conservation of energy	KE₁ + PE₁ = KE₂ + PE₂
Power	P = W/t = Fv

Energy conservation is one of the most frequently tested concepts. If a ball rolls off a table, kinetic energy at the bottom equals potential energy at the top (assuming no friction). Set them equal and solve.

Section 2: Thermodynamics

Thermodynamics covers heat, temperature, and energy transfer. This connects directly to nuclear reactor design — in my PhD research, understanding heat transfer was as critical as understanding the nuclear reactions themselves.

The Laws of Thermodynamics

• Zeroth Law: If A is in thermal equilibrium with B, and B is in thermal equilibrium with C, then A and C are in equilibrium. (This defines temperature.)
• First Law: Energy is conserved. ΔU = Q − W, where ΔU is change in internal energy, Q is heat added, W is work done by the system.
• Second Law: Entropy of an isolated system never decreases. Heat flows spontaneously from hot to cold, never the reverse.
• Third Law: As temperature approaches absolute zero, entropy approaches a minimum constant.

Heat Transfer

Three mechanisms of heat transfer appear on the test:

• Conduction: heat transfer through direct contact (metals conduct well; wood conducts poorly)
• Convection: heat transfer through fluid motion (hot air rising, ocean currents)
• Radiation: heat transfer via electromagnetic waves (the Sun heats Earth through radiation across vacuum)

Specific Heat

Q = mcΔT, where Q is heat added (in joules), m is mass (kg), c is specific heat capacity (J/kg·°C), and ΔT is temperature change. Water has an unusually high specific heat (4,186 J/kg·°C), which is why oceans moderate climate and why water is used as a reactor coolant.

Section 3: Electricity and Magnetism

Ohm's Law and Circuits

Concept	Formula	Units
Ohm's Law	V = IR	V = volts, I = amperes, R = ohms
Power	P = IV = I²R = V²/R	Watts
Series resistance	Rₜₗₜₕ = R₁ + R₂ + ...	Adds directly
Parallel resistance	1/Rₜₗₜₕ = 1/R₁ + 1/R₂ + ...	Reciprocal sum

Know the difference between series and parallel circuits conceptually. In series, the same current flows through all components; voltage divides. In parallel, the same voltage is across all components; current divides.

Electric and Magnetic Fields

The electric force between two charges follows Coulomb's law: F = k(q₁q₂)/r², where k = 8.99 × 10⁹ N·m²/C². Like charges repel; opposite charges attract.

Magnetic fields are generated by moving electric charges. A current-carrying wire creates a magnetic field around it (right-hand rule: wrap your right hand around the wire with the thumb pointing in the direction of current flow; your fingers indicate the field direction). The AFOQT tests conceptual understanding of these relationships, not numerical computation.

Section 4: Waves and Optics

Wave Fundamentals

Concept	Formula / Definition
Wave speed	v = fλ (speed = frequency × wavelength)
Frequency	Cycles per second; measured in Hz
Wavelength	Distance between successive peaks; measured in meters
Period	T = 1/f (time for one complete cycle)
Speed of light	c = 3 × 10⁸ m/s in vacuum

Transverse waves oscillate perpendicular to the direction of travel (light, water waves). Longitudinal waves oscillate parallel to the direction of travel (sound). The electromagnetic spectrum from longest to shortest wavelength: radio, microwave, infrared, visible, ultraviolet, X-ray, gamma ray.

Snell's Law and Optics

Snell's Law: n₁sin(θ₁) = n₂sin(θ₂), where n is the index of refraction and θ is the angle from the normal. Light bends toward the normal when entering a denser medium (higher n) and away when entering a less dense medium.

Key optics concepts: reflection (angle of incidence equals angle of reflection), refraction (bending at an interface), total internal reflection (light cannot exit a denser medium above the critical angle — this is the principle behind fiber optics).

Section 5: Nuclear Physics (My Home Turf)

This is where my PhD gives students a real edge. Nuclear questions on the AFOQT test basic concepts that I work with at a research level daily — which means I can explain them at exactly the depth the test requires without overcomplicating.

Fission and Chain Reactions

Nuclear fission is the splitting of a heavy nucleus (like uranium-235 or plutonium-239) by a neutron into smaller fission products, releasing energy and additional neutrons. Those neutrons can then cause more fissions — this is the chain reaction. The energy released comes from the mass defect: the fission products have slightly less total mass than the original nucleus, and that mass difference appears as energy via E = mc².

Radioactive Decay and Half-Life

Radioactive nuclei decay spontaneously. The half-life (t₁/₂) is the time it takes for half of a sample to decay. After one half-life, 50% remains. After two half-lives, 25% remains. After n half-lives, (1/2)ⁿ of the original amount remains.

Decay Type	Particle Emitted	Penetration	Shielding
Alpha (α)	Helium nucleus (2p + 2n)	Low (stopped by paper)	Paper or skin
Beta (β)	Electron or positron	Medium	Plastic, aluminum
Gamma (γ)	High-energy photon	High	Lead, thick concrete