Essential MCAT Physics Equations | Study Guide

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Reviewed by:

Jonathan Preminger

Former Admissions Committee Member, Hofstra-Northwell School of Medicine

Reviewed: 3/26/24

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Preparing for the physics section on the MCAT and don’t know which equations to prioritize? Keep reading for a quick summary of important MCAT physics equations.

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Are you gearing up for the MCAT and feeling a bit anxious about the physics section? You're not alone. Many aspiring doctors find themselves wondering why physics is so heavily emphasized on this pivotal exam. 

The truth is that a solid understanding of physics is one of the first steps of getting into medical school. From X-rays and MRIs to blood pressure and neural circuits, the principles of physics lay the foundation of modern medicine. 

But fear not! We've got you covered with a comprehensive guide to the key physics equations you need to know for the MCAT. By focusing your study time on these important concepts, you'll be well on your way to acing the physics section and taking one step closer to your dream of becoming a physician.

MCAT Physics Equations You Need to Know

There are several physics topics that you could be tested on the MCAT, including work, kinematics, and sound. Below we summarize the key physics equations for each topic that you could be tested on during the MCAT.

Work, Force, and Energy

Work, force, and energy are the bread and butter of physics. Work is a form of energy that applies force to an object to displace it.

Newton’s 2nd Law

F = m x a

The net force (F) on an object can be calculated from the product of the object’s mass (m) and acceleration (A).

Work Done by Constant Force

W = F x d x cosθ 

The work (W) done on an object by a constant force is a product of the magnitude of the force (F) and the direction in which the object is displaced (d) due to this force. Cosine theta (cosθ) is the angle between the object and the force acting on it. 

Work-Kinetic Energy Theorem

Wnet = ΔKE

The total work (Wnet) done by combined forces is proportional to the change of kinetic energy (ΔKE) of an object.

Kinetic Energy 

KE = 1/2 x m x v²

Kinetic energy is proportional to the mass (m) of an object and the square of its velocity (v). 

Potential Energy

PE = m x g x h

The gravitational potential energy (PE) of an object is proportional to the object’s mass (m) and height (h) and to the acceleration of gravity (g = 9.8 m/s²).

Power

P = ΔW/Δt

Power is equal to the amount of work done (W) divided by the time (t).

An Example of this Equation on the MCAT

Work-Energy Theorem: W = ΔKE

Kinematics

Kinematics is a field of physics that is all about the motion of objects and systems. Unlike the work and energy section above, kinematic equations do not take into account the forces that cause motion. 

Velocity 

V = V_­0 + at 

This equation denotes the velocity of an object under constant velocity at time (t), which equals the initial velocity (V_­0) plus the product of acceleration (a) and the time interval.

V²= V₀² + 2aΔx

This equation uses the initial velocity, acceleration, and displacement (Δx) to solve for the final velocity. 

Displacement

Δx= V_­0 + ½ at²

This equation uses the acceleration, initial velocity, and time interval to solve for displacement for an object under constant acceleration.

An Example of this Equation on the MCAT

Displacement with constant acceleration: Δx = v0t + ½at²

Fluid Mechanics

Fluid mechanics is concerned with the mechanisms and forces related to liquids, gases, and plasmas.

Pascal’s Law 

P = F/A

Pascal’s law states that pressure exerted on fluid at rest is transmitted equally in all directions of the container holding said fluid. Pressure is equal to the applied force (F) divided by the area of contact (A).

Bernoulli’s equation

P + ½ pV² + pgh = constant

Bernoulli’s equation describes how the velocity of the fluid through a tube relates to the pressure of the fluid. P is hydrostatic pressure, p is the fluid density, V is velocity, g is the gravitational acceleration (9.8 m/s²), and h is the height of the fluid. 

Density

p = m/V

The density (p) of a substance is proportional to its mass (m) per unit volume (V).

Specific Gravity

SG = p_subsance/p_water 

Specific gravity is the ratio of the density of a substance (p_subsance) compared to a reference substance (p_water).

Buoyant force

F_b = p_fluid  x V x g

Buoyant force (F_b) is the upward force a fluid exerts on an object. V is the object’s volume, p is the object’s density, and g is the gravitational acceleration.

Hydrostatic pressure

P = P₀ + ρgz

Hydrostatic pressure (P) is the pressure (P₀) exerted by a fluid at rest due to the force of gravity (g).

An Example of this Equation on the MCAT

Archimedes' Principle (Buoyant Force): FB = ρfluidVg

Electrostatics and Circuits

This section focuses on how charged particles interact with each other in systems such as circuits.

Coulomb’s Law

F = - k * q₁q₂/r²

According to Coulomb’s law, like charges repel and opposite charges attract. The force of attraction is proportional to the production of the charges (q₁q₂); it is inversely proportional to the square of the distance between the charges (r²)

Ohm’s Law

V = IR

Ohm’s law states that voltage (V) across a conductor is proportional to current (I) and inversely proportional to resistance (R). You can rearrange this equation to solve for current or resistance.

Current

I = Q/t

This formula defines how charge flows through an electric circuit as a current (I). It is the quantity of charge flowing (Q) in a time period (t).

Resistance

R = pl/A

This equation gives the resistivity of a wire. It corresponds to the resistivity of the material (p), the length of the wire (l), and the cross-sectional area of the wire (A).

Capacitors in Series

R_T = R₁ + R₂ + …. + R_N

This equation denotes total resistance (R_T) in a series combination, in which the resistors are connected end-to-end in a circuit. 

Capacitors in Parallel

1/R_T = 1/R₁ + 1/R₂ + …. + 1/R_N

This formula denotes total resistance (1/R_T) in a series combination, in which the resistors’ terminals are connected to the same two nodes.

An Example of this Equation on the MCAT

Electric Potential Energy: U = kq1q2/r

Thermodynamics

Thermodynamics is a field of physics that describes how heat relates to work and energy.

Heat phase during change

q = m * L_x

This equation describes the heat (q) required to cause a phase change of a sample of mass m. L_x can be either the latent heat of fusion or the latent heat of vaporization and is the amount of heat necessary to cause a change between a solid and liquid and a liquid and vapor, respectively.

An Example of this Equation on the MCAT

First Law of Thermodynamics: ΔU = Q - W

Light

Light is electromagnetic radiation detected by an organism’s eye.

Snell’s law

n₁ x sin θ₁ = n₂ x sin θ₂

This equation describes the relationship between refraction (n) and angles of incidence (sin θ) when light passes a boundary separating two media.

Lens equation

1/d₀ + 1/di = 1/f

This equation is used to calculate image distance and describes the relationship between object distance (d_o), image distance (d_i), and focal length (f).

An Example of this Equation on the MCAT

Thin Lens Equation: 1/f = 1/do + 1/di

Sound

Sound is a vibration that propagates through air, liquid, and other mediums as a longitudinal wave.

Wave Velocity

V = f x λ

This equation uses the frequency (f) and wavelength (λ) of a wave to calculate the wave’s velocity (V).

An Example of this Equation on the MCAT

Doppler Effect: fo = fs[v/(v±vs)]

FAQs: Physics on the MCAT

Below are some frequently asked questions about physics on the MCAT.

1. Do You Need to Know All Physics Equations on the MCAT?

While it's not necessary to memorize every single physics equation for the MCAT, it's highly recommended to commit the key equations to memory. Focusing on the most important and frequently tested equations can save you valuable time during the exam.

2. Do You Have to Memorize Equations for the MCAT Physics Section?

Yes, you will need to memorize most equations for the MCAT physics section, as a formula sheet is not provided. To be well-prepared, it's best to memorize the equations beforehand to efficiently tackle the physics problems on the MCAT.

3. How Should You Memorize Equations for the MCAT Physics Section?

One of the most effective ways to memorize equations for the MCAT physics section is by consistently practicing questions. Regularly applying the equations to solve problems helps reinforce your understanding and makes recalling them during the exam more natural.

4. Is the MCAT Physics Heavy?

Physics questions make up a significant portion of the Chemical and Physical Foundations of Biological Systems section, which is one of the four sections on the MCAT. Expect around 25% of the questions to be physics-focused, which translates to approximately 57 questions out of the 230 total questions on the MCAT.

Final Thoughts

Mastering the physics equations for the MCAT may seem like a formidable task, but with the right approach and mindset, you can conquer this challenge and boost your score on test day. 

Remember, understanding the fundamentals, memorizing key equations, and practicing consistently are the keys to success. Don't be afraid to break down complex problems into manageable steps, pay close attention to units, and seek help when needed. 

By dedicating yourself to studying these physics concepts and applying them to real-world scenarios, you'll not only excel on the MCAT but also lay the foundation for a successful career in medicine. With determination and the right tools at your disposal, you've got this!