The MCAT Physics Equations You Must Know in 2020

Updated: September 29, 2020


What MCAT physics equations do you need to know? The Chemical and Physical Foundations of Biological Systems section of the MCAT, or the chemistry and physics section for short, can be a challenge, especially if you sit down to take the MCAT unprepared. There are certain physics equations that you must know in order to ace this first section of the MCAT. After all, the processes that take place within organisms follow the laws of physics! This blog includes an overview of every physics equation that you need to know for the MCAT and our tips for how to effectively use them on the test day!

Here's what you'll learn:

How much physics is on the MCAT?

Essential physics equations for the MCAT

Tips for how to use physics equations during the MCAT

Frequently Asked Questions

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. What do we mean by introductory physics? You will not be using overly complex physics equations on this section of the MCAT, but rather, you will need to be able to apply physics concepts from your two-semester 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 physics questions. When to start studying for the MCAT will depend, in part, on how much knowledge you have retained from your introductory physics courses.

The AAMC has identified your understanding of how complex living organisms transport materials, sense their environment, process signals, and respond to changes – in terms of physical principles – as a foundational concept on the MCAT. Approximately 40% of the chemistry and physics section will focus on this foundational concept and will include the following physics related content categories:

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 on the MCAT with the AAMC’s guide "What is on the MCAT Exam?"

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Essential physics equations for the MCAT

There are a lot of physics equations out there, but which ones do you actually need to know for the MCAT? Keep reading to get a look at each 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 = ½ kx2

  • 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: PTotal = P1 + P2 …

  • Dalton’s Law states that the total pressure (PTotal) 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

Do you want to learn about the best MCAT study schedule? Watch our video:

Tips for how to use physics equations during the MCAT

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

Yes, there are a fair number of physics equations that you will need to memorize, and thoroughly understand how to utilize, for the MCAT, but they 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 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. Keep in mind that the physics equations you will need are simple: if you find yourself doing a complicated multi-step problem, and you have already spent several minutes on calculations, you need to reassess your approach.


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. You start to panic and worry that you just wasted five precious minutes and you still don’t know the answer. 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! Another tip: get comfortable re-arranging equations to solve for a particular variable to avoid errors on test day.

Tip #3: Apply your physics knowledge

Physics concepts will be tested within the context of living systems. Therefore, the types of questions you may have seen on your introductory level physics exams in college will likely not appear on the MCAT. 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. If you don’t know how a physics concept applies to living systems, this is something you will want to investigate.

For more MCAT tips, be sure to also utilize our MCAT psychology and sociology, MCAT CARS, and MCAT biology questions and biochemistry tips specifically geared towards acing each section of the MCAT! Don't forget to check out our foolproof MCAT CARS strategy!

Worried about your MCAT score? Check out our video:

Frequently Asked Questions

1. How long is the chemistry and physics section of the MCAT and what is the format?

The chemistry and physics section is the first of the four MCAT sections. For this section you will have 95 minutes to answer 59 questions. Out of these 59 questions, 44 are passage based. You will be presented with ten passages about chemistry and physics topics and you will be asked four to seven passage-based questions after each passage. There will also be 15 stand-alone discrete questions dispersed in between passages. Interested in a detailed breakdown of how every minute will be allocated on test day? Check out our blog "How Long is the MCAT?"

2. How can I use a diagnostic exam to determine how much physics I will need to study for the MCAT?

Before you can start studying for the MCAT, you will need to understand your baseline. To do this, you need to take a full-length MCAT diagnostic test. The goal is to understand exactly where you stand as you embark on your MCAT preparations. For your diagnostic, it's best to use a full-length exam from the AAMC website. Ensure you complete your practice exam in one sitting in an environment that mimics test-day conditions. As you review the results of your diagnostic, assess your strengths and areas for improvement. How did you do on the physics-related questions? Did you draw a blank when it came to certain physics equations or content areas? Were you able to connect your physics knowledge to questions about living organisms and body systems? Be honest with yourself in regards to your comfort level with MCAT physics as you review our blog that helps you determine the common question “when should I take the MCAT?" After setting a goal MCAT test date, map out your MCAT preparations using our comprehensive MCAT study schedule guide.

3. What are some techniques for memorizing the physics equations I will need on test day?

As you study for the MCAT, you may find that the traditional methods for memorizing equations, such as making flashcards, are not working for you. What else can you try? Here are some additional techniques to consider working into your MCAT preparation:

  • Write the equation down several times on a piece of paper until you can recite it out loud without referencing your study materials.
  • Try to expand an equation into a sentence that explains what the equation tells you.
  • Complete several practice problems that require use of the equation.
  • Try grouping several equations together by topic to see similarities between equations that you are struggling with and ones that you have already mastered.
  • Ask a friend if they have developed any catchy mnemonic devices to remember the physics equations you will need for the MCAT.

Remember, truly understanding an equation will be key in remembering it. For any equations that you are struggling with, go into depth for each part of the equation and work to understand how each part works together. You can also try going back in your notes and reviewing any equations relating to foundational concepts that you learned previously. Knowledge gaps in topics that you have already covered may be hindering your ability to learn new equations. If you are really struggling, you can look into an MCAT tutor and remember to research what is a good MCAT score.

4. Can I use a calculator as I solve physics equations on the MCAT?

You will not be able to use a calculator on any sections of the MCAT, which means that it is important that you do not complete sample questions or practice MCAT exams with a calculator. It is important that you set yourself up for success by completing your MCAT preparations under conditions that will mimic those of test day. Use the months leading up to your MCAT to build up your efficiency in doing mental calculations and in doing math by hand.

5. Will I need to know how to draw free body diagrams for the MCAT?

The MCAT is a multiple-choice test and does not contain any free-response questions where your knowledge of how to draw diagrams will be tested. That being said, a basic knowledge of how to draw free body diagrams to do force calculations will certainly come in handy when solving multiple-choice questions related to physics, so do not neglect practicing this skill.

6. Is AP Physics sufficient for conquering physics-related MCAT questions?

The answer to this question will of course depend on how well you did in your AP Physics course. AP Physics should give you the same introductory physics knowledge that you would have been exposed to through a university introductory physics course. Use your diagnostic exam to really assess your comfort level with physics equations and physics concepts on the MCAT. If you have a good baseline score for the chemistry and physics section of the MCAT, then you can build on your AP Physics knowledge by ensuring you still know the necessary equations and by reinforcing key concepts as you study. You will likely still need to investigate how fundamental physics concepts relate to living systems, as this may not have been emphasized in your AP Physics course.

7. How come only these equations are listed as essential? Don’t I need to know more?

Yes, you may need others, but you can derive or deduce them more easily based on these essential ones. If you don’t know these essential ones, you will not be able to derive or deduce the others.

8. When should I take the MCAT?

Make sure to take the exam when you are ready. This typically means that you're consistently scoring in the 90th percentile in your practice exams. 

Conclusion

Why is physics on the MCAT? Physics is just one of the many building blocks that you will need as a medical student to learn about the physiological functions of the respiratory, cardiovascular, and neurological systems in health and disease. Therefore, the chemistry and physics section of the MCAT is your opportunity to demonstrate your understanding of how fundamental physics concepts will apply to your future career in medicine. A key piece of your success on the MCAT will be to start learning, and truly understanding, each of the physics equations outlined in this blog.

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