The MCAT Physics Equations You Must Know

How Much Physics is on the MCAT?

You may be wondering just how much physics you will see on the MCAT? Your physics knowledge will come into play within the first section of the MCAT: Chemical and Physical Foundations of Biological Systems. According to the AAMC, you can expect approximately 25% of the questions in this section to relate to introductory physics.

You will be using physics concepts from your introductory level university physics course to demonstrate a broad understanding of the dynamics within living systems. You can expect to see physics related questions that are passage-based as well as a few stand-alone discrete MCAT physics questions.

Although physics doesn’t make up the majority of the test, it’s still important to identify what topics you can expect and review them. Here’s what one of our admissions consultants experienced when preparing for the MCAT physics section:

“I had just taken biochemistry in the spring semester preceding my MCAT and had also concurrently taken general biology in the fall, so these were my strongest science sections. My weakest section was physics. The MCAT strategy that worked for me was knowing what I was up against (question subject breakdown) and focusing on what I could realistically review in the time that I had. I didn’t have time to relearn all of general physics and the number of physics question is about 5% of the exam … I focused on refining my strongest points, reviewing topics I had grasped previously, and focusing on high yield for the items I didn’t know.” – Dr. Monica Taneja, MD, University of Maryland School of Medicine.

Approximately 40% of the chemistry and physics section will focus on these foundational concepts and will include the following MCAT high-yield topics:

• 4A – Translational motion, forces, work, energy, and equilibrium in living systems
• 4B – Importance of fluids for the circulation of blood, gas movement, and gas exchange
• 4C – Electrochemistry and electrical circuits and their elements
• 4D – How light and sound interact with matter
• 4E – Atoms, nuclear decay, electronic structure, and atomic chemical behavior

Take a closer look at the content categories with the AAMC’s guide "What is on the MCAT Exam?"

Essential Physics Equations for the MCAT

Keep reading to get a look at each MCAT physics equation that the AAMC recommends you know, broken down by content category:

4A – Translational motion, forces, work, energy, and equilibrium in living systems

This content category focuses on motion and its causes, as well as various forms of energy and their interconversions.

1. Newton’s Second Law: F = ma

• This equation is Newton’s second law, which states that the net force (F) on an object is proportional to the object’s mass (m) and acceleration (a).

2. Work By a Constant Force: W = Fd cosθ

• This equation describes the work energy principle, or the work (W) done by a constant force (F) on an object that is moving in a specific direction. In this equation, d is the distance the object moves while the force was exerted on it, and cosine theta (cosθ) is the angle between the force and the displaced object.

3. Work Kinetic Energy Theorem: Wnet = ΔKE

• This theorem states that the net work (Wnet) on a system is equal to the change in kinetic energy (ΔKE) of a moving object, particle, or system of objects moving together.

4. Kinetic Energy: KE = ½ mv²

• Kinetic energy (KE) is a form of energy associated with the motion of an object. This energy is related to a certain mass (m) moving at a particular velocity (v). The kinetic energy is proportional to the velocity squared (v²).

5. Potential Energy: PE = mgh

• This equation describes gravitational potential energy (PE), which depends on the position of an object. To use this equation, you will need the mass of the object (m), gravitational acceleration (g), which is 9.8 m/s² at the surface of the Earth, and the height of the object in meters (h).

6. Potential Energy: PE=½kx²

• An elastic force is a force that results from stretching or compressing an object, such as a spring. In this potential energy (PE) equation, k is the spring constant and x is the distance the spring is stretched. The spring constant relates to the spring’s stiffness.

4B – Importance of fluids for the circulation of blood, gas movement, and gas exchange

This content category focuses on the behavior of fluids as it pertains to the functioning of the pulmonary and circulatory systems.

1. Pascal’s Law of Hydrostatic Pressure: P = ρgh

• This law applies to static fluids and relates pressure to depth. The pressure in a liquid at a given depth is called the hydrostatic pressure and this pressure increases as depth below the surface increases. In this equation, P is the hydrostatic pressure, ρ is the density of the liquid, g is gravitational acceleration (9.8 m/s²), and h is the depth/height of the liquid in meters.

2. Continuity Equation: A∙v = constant

• Continuity of flow is a fundamental principle of fluids. Because mass is conserved in a fluid system, continuity of flow also exists. In this equation, A is the cross-sectional area of flow and v is the velocity. If the cross-sectional area in a fluid system changes, the velocity will change in a way that is inversely proportional in order to maintain continuity.

3. Bernoulli’s Equation: P + ½ρv² + ρgh = constant

• This equation allows you to analyze a fluid as it moves through a tube and relates the velocity of the fluid to its pressure. For a horizontal tube that changes in diameter, regions where the fluid is moving fast will be under less pressure than regions where the fluid is moving slow. Bernoulli's equation applies principles of energy conservation to a flowing fluid. In this equation, P is the hydrostatic pressure, ρ is the density of the liquid, v is the velocity, g is gravitational acceleration (9.8 m/s²), and h is the height of the liquid in meters.

4. Ideal Gas Law: PV = nRT

• The ideal gas law describes the behavior of an ideal gas and combines together ideas found in various other gas laws. In this equation, P is the pressure of the gas, V is the volume in liters, n is amount of gas in moles, R is the universal gas constant, and T is temperature in Kelvin. The value of R will depend on the units you use in this equation.

5. Boyle’s Law: PV = constant, P₁V₁ = P₂V₂

• This gas law states that the pressure (P) of gas is inversely related to its volume (V) at a constant temperature. Boyle’s Law allows you to calculate how the volume of a gas will change as the pressure exerted on it changes, and vice versa.

6. Charles’ Law: V/T = constant, V₁/T₁ = V₂/T₂

• This gas law states that the volume (V) of gas is directly related to its temperature (T) at a constant pressure. Charles’ Law allows you to calculate how the volume of a gas will change as its temperature changes, and vice versa.

7. Avogadro’s Law: V/n = constant, V₁/n₁ = V₂/n₂

• This gas law relates the volume of a gas to the number of moles within the gas. The volume (V) of a gas is directly related to number of moles (n) within it. At constant temperature and pressure, a larger number of moles will take up a larger volume. Avogadro’s Law allows you to calculate how the volume of a gas will change as the number of moles change, and vice versa.

8. Dalton’s Law of Partial Pressures: P_Total = P₁ + P₂ …

• Dalton’s Law states that the total pressure (P_Total) exerted by a gas mixture is the sum of the individual pressures (P₁, P₂, etc.) exerted by each gas in the mixture.

4C – Electrochemistry and electrical circuits and their elements

This content category emphasizes the nature of electrical currents and voltages, how energy can be converted into electrical forms that can be used to perform chemical transformations or work. In addition, the category includes how electrical impulses can be transmitted over long distances in the nervous system.

1. Coulomb’s Law: F = k∙(q₁q₂/r²)

• This law quantifies the force between two electrically charges particles. The electrical force (F) of repulsion or attraction between the particles is proportional to the product of the charges (q) and is inversely proportional to the square of the distance between them (r²). In this equation, k is Coulomb’s constant.

2. Constant Current: I = ΔQ/Δt

• This equation allows you to calculate the electrical current (I) through a circuit as electric charge (ΔQ) flows over a time duration of Δt.

3. Ohm’s Law: I = V/R

• Ohm’s Law relates the current (I) flowing through a circuit to the voltage (V) and resistance (R). The current is equal to the voltage divided by the resistance in ohms.

4. Resistivity: ρ = R∙A/L

• This resistivity equation demonstrates that resistivity (ρ) of a material, such as a wire, is equal to the resistance (R) of the material in ohms, multiplied by its cross-sectional area (A), and divided by its length (L).

4D – How light and sound interact with matter

This content category focuses on the properties of light and sound, how the interactions of light and sound with matter can be used by an organism to sense its environment, and how these interactions can also be used to generate structural information or images.

1. Photon Energy: E = hf

• The energy (E) of a photon within an electromagnetic wave is directly related to the wave frequency (f). In this equation, h is Planck’s constant.

2. Snell’s Law: n₁sinθ₁ = n₂sinθ₂

• Snell’s Law describes the change in direction of a light ray as it moves from a medium with one refractive index (n₁) to another medium with a different refractive index (n₂). The angle (sinθ₁) of incidence towards the surface and the angle (sinθ₂) of refraction are measured relative to a surface normal.

3. Lens Equation: 1/f = 1/p + 1/q

• The bending of light rays through a thin lens is summarized by the Lens Equation. In this equation, f is the focal length of the lens, p is the distance of the object from the lens, and q is the distance of the image from the lens. You will need to know the sign conventions for this equation, or when certain values will be positive or negative: for a convex lens the focal length will always be positive, for a concave lens the focal length will always be negative.

4E – Atoms, nuclear decay, electronic structure, and atomic chemical behavior

This content category focuses on sub-atomic particles, the atomic nucleus, nuclear radiation, the structure of the atom, and how the configuration of any particular atom can be used to predict its physical and chemical properties.

• The AAMC does not reference any specific physics equations that you will need to know for this last content category in the Chemical and Physical Foundations of Biological Systems section of the MCAT.

If you are feeling overwhelmed by the number of physics equations that you will need to know for the MCAT, be sure to check out our helpful tips below. For a look at mean scores and percentile ranks for the chemistry and physics section of the MCAT, take a look at our blog How Hard is the MCAT? 

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How to Use Physics Equations on the MCAT

Tip #1: Remember, you do not need to be a physics genius to do well on the MCAT

The equations above are only a small portion of the physics equations that exist in the universe. They are also not the most complex of physics equations and generally apply to problems that can be solved in only a few steps. The questions on the chemistry and physics section of the MCAT will revolve around simple physics equations and foundational concepts.

"The MCAT Physics section covers a vast range of concepts, and even with a solid foundation, I encountered a lot of difficulties applying the specific details and nuances needed to answer questions quickly. The time constraint adds another layer of difficulty for me ... Building a strong conceptual foundation was crucial. I started with Khan Academy to solidify core concepts, then moved to ... deeper understanding and practice. Creating detailed diagrams for each topic and an equation sheet with key formulas helped me visualize and recall information quickly. Explaining concepts to myself out loud also solidified my understanding." – Dr. Cathleen Kuo, MD

The key is to understand when to make use of these equations and how to use them quickly and confidently. After memorizing each physics equation that you will need to know, completing as many MCAT chemistry and physics practice problems as you can will help you to gain an understanding of how to apply these equations.

“For anyone taking the MCAT or retaking the MCAT I definitely recommend the AMCAS bundle of practice exams and all of that. That's what I mainly used to prepare but I took kind of the average of the score that I was getting and used use that as my gauge … [you’ll have] a pretty good idea of where your performance was across a couple of those practice tests.” – Allison, former BeMo student and current student at Dell Medical School.

Tip #2: Watch out for units

We’ve all been there: you just spent five minutes on lengthy calculations and, in glancing down at the answer choices, your solution is not amongst the possible answers. Often times, a quick unit conversion can reveal the correct answer; or you may have simply used the incorrect units in your equation. Understanding how to convert between units and ensuring that you can do this quickly without a calculator, is essential for the chemistry and physics section of the MCAT! Our admissions expert, Dr. Noah Heichel, DO, recommends using active learning techniques such as flashcards to memorize important formulas and equations.

Dr. Neel Mistry, another of our MD experts, says he practiced with real-life examples:

“The hardest part of physics was remembering the different formulas and knowing which one to use when … [I learned] about Physics topics using real-life examples (i.e., pendulum, spring, etc.)” – Dr. Neel Mistry, MD.

Our admissions expert Dr. Cathleen Kuo also found ways to creatively study physics topics outside her usual studying hours.

"I incorporated short breaks with activities like going for walks or listening to science podcasts. I also found physics-related documentaries and engaging YouTube channels that helped me learn in a more interactive way. Discussing challenging problems with classmates added a social aspect to studying, making it more fun and motivating." – Dr. Cathleen Kuo, MD.

Tip #3: Apply your physics knowledge

Physics concepts will be tested within the context of living systems. There will be no in-depth 30-minute long physics calculations. It is important to understand that you will be applying fundamental physics concepts to the human body, for example, to a passage about the flow of fluids through the aorta. As you study physics concepts for the MCAT, focus on the application of these physics concepts to the human body.

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