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MCAT Physics: Every Formula, Concept & Strategy You Need

Physics is the most feared section on the MCAT — and the most misunderstood. You do not need calculus. You do not need to memorize 200 equations. You need 40 core equations, rock-solid conceptual understanding, and the ability to apply physics reasoning to medical scenarios. This guide gives you all three.

AI-generated content. This guide was written by MedAI's AI and is intended as a study aid. Always cross-reference with your official course materials, textbooks, and instructor guidance before your exam.

How Physics Is Actually Tested on the MCAT

The Chemical and Physical Foundations section (C/P) tests physics primarily through passage-based clinical scenarios: blood pressure and fluid dynamics, sound in medical imaging, optics in diagnostic tools, electricity in electrocardiography. The math rarely involves more than simple algebra.

The MCAT Physics Philosophy

For most physics questions, set up the equation, identify which variables change and which stay constant, and predict the direction of the effect — without solving numerically. Half the physics questions on the MCAT can be answered by knowing relationships (doubling A quadruples B) rather than plugging and chugging.

Module 1: Kinematics & Forces

Concept	Key Equation	Clinical/MCAT Context
Kinematics (constant acceleration)	v = v₀ + at; x = v₀t + ½at²; v² = v₀² + 2ax	Projectile motion; falling objects
Newton's Second Law	F = ma	Force on cartilage, bone fracture mechanics
Friction	f = μN	Static vs kinetic friction in biomechanics
Work	W = Fd·cosθ	Work done by muscles against gravity
Kinetic Energy	KE = ½mv²	Energy in collisions; trauma biomechanics
Potential Energy	PE = mgh	Gravitational PE; spring PE = ½kx²
Power	P = W/t = Fv	Metabolic rate; cardiac power output
Torque	τ = rF·sinθ	Lever mechanics; musculoskeletal joints

Module 2: Fluid Dynamics (Highest Yield for MCAT)

Fluid mechanics is the single highest-yield physics topic on the MCAT because it directly models blood flow, respiratory mechanics, and intravenous fluid delivery.

Concept	Equation	Clinical Application
Density	ρ = m/V	Urine specific gravity; blood density
Pressure	P = F/A; P = ρgh (hydrostatic)	Blood pressure (mmHg); hydrostatic pressure in capillaries
Continuity Equation	A₁v₁ = A₂v₂	Blood speeds up at stenosis; arterial narrowing
Bernoulli's Equation	P + ½ρv² + ρgh = constant	High velocity → low pressure at stenosis (explains atherosclerotic effects)
Poiseuille's Law	Q = πr⁴ΔP / 8ηL	Blood flow: quadrupled by doubling vessel radius; key for vasoconstriction/dilation
Viscosity	η (eta) — resists flow	Anemia lowers viscosity; polycythemia increases it
Buoyancy	F_b = ρ_fluid × V_displaced × g	Objects float when density < fluid; relevant in pulmonary ARDS
Surface Tension	γ = F / 2L; Laplace: ΔP = 2γ/r	Alveolar collapse in premature infants (↓ surfactant → ↑ surface tension)

Poiseuille's Law is Massively Tested

Resistance to blood flow R ∝ 1/r⁴. Halving a vessel radius INCREASES resistance by 16×. This explains why mild arterial stenosis dramatically reduces blood flow and why vasodilators have outsized effects. Know this relationship cold.

Module 3: Thermodynamics & Gases

Concept	Equation	Clinical Relevance
Ideal Gas Law	PV = nRT	Lung volumes; anesthesia gas delivery
Boyle's Law	P₁V₁ = P₂V₂ (constant T)	Inspiration: thorax expands → volume ↑ → pressure ↓
Charles's Law	V₁/T₁ = V₂/T₂ (constant P)	Gas volume changes with temperature
First Law of Thermodynamics	ΔU = Q − W	Energy conservation in metabolic processes
Entropy (Second Law)	Spontaneous = ΔS_universe > 0	Protein folding; membrane formation driven by entropy
Gibbs Free Energy	ΔG = ΔH − TΔS	ΔG < 0 = spontaneous reaction; coupled reactions in metabolism
Heat Transfer	Q = mcΔT	Body temperature regulation; specific heat of water = 1 cal/g°C

Module 4: Waves, Sound & Light

Concept	Equation/Principle	Clinical Context
Wave speed	v = fλ	Ultrasound: frequency × wavelength = speed in tissue
Sound intensity (decibels)	β = 10·log(I/I₀)	Hearing tests; noise-induced hearing loss
Doppler Effect	f_obs = f_s(v ± v_obs)/(v ∓ v_s)	Doppler ultrasound: blood flow velocity measurement
Snell's Law	n₁sinθ₁ = n₂sinθ₂	Refraction of light in eye (cornea, lens)
Thin lens equation	1/f = 1/d_o + 1/d_i	Corrective lenses; near/farsightedness
Power of lens	P = 1/f (in diopters)	Prescription glasses; converging vs diverging lenses
Total internal reflection	sinθ_c = n₂/n₁	Fiber optics in endoscopy

Module 5: Electricity & Magnetism

Concept	Equation	Clinical Context
Ohm's Law	V = IR	Neuron membrane potential; cardiac conduction
Power dissipation	P = IV = I²R = V²/R	EKG electrode power; electrical safety
Capacitance	C = Q/V; Q = CV	Cell membrane acts as capacitor; charge storage across membrane
Series/parallel circuits	Series: R_total = ΣR; Parallel: 1/R = Σ(1/R)	Ion channel conductances in neurons (parallel)
Coulomb's Law	F = kq₁q₂/r²	Electrostatic interactions between charged proteins
Magnetic Force	F = qv × B	MRI: charged nuclei in magnetic field precess; basis of NMR

Module 6: Radioactive Decay & Nuclear Physics

Alpha decay: nucleus emits α particle (⁴₂He). Atomic number decreases by 2, mass number by 4. Dangerous if inhaled (radon gas, alpha emitters).
Beta decay (β⁻): neutron → proton + electron. Atomic number increases by 1. Used in PET scan tracers.
Beta decay (β⁺): proton → neutron + positron. Atomic number decreases by 1. FDG-PET imaging.
Gamma radiation: high-energy photons released after nuclear decay. Most penetrating. Used in radiation therapy.
Half-life: t½ = 0.693/λ. After n half-lives, fraction remaining = (1/2)ⁿ.
MCAT favorite: ¹⁴C dating (t½ = 5,730 years), ¹³¹I thyroid therapy (t½ = 8 days), ⁹⁹ᵐTc imaging (t½ = 6 hrs).

Physics Problem-Solving Protocol

1Identify what type of problem it is (fluid, wave, circuit, kinematics, thermodynamics)
2Write down what is given and what you need to find
3Select the relevant equation — if you do not know it exactly, derive it from relationships
4Identify constant variables and predict the direction of change qualitatively first
5Solve algebraically, then plug in numbers only at the final step
6Check: does the magnitude make physical sense? Are units correct?