Needed for admission to U.S. medical schools, the Medical College Admissions Test (MCAT) measures a student's knowledge of core concepts in the natural sciences, social and behavioral sciences, and humanities.
Although much of the test is related to life sciences and psychology, in order to do well on the Chemical and Physical Foundations of Biological Systems section of the MCAT, students need an understanding of physics and basic physics equations.
In fact, 25% of this subtest is based on introductory physics, so knowing basic physics equations is important. Hence, it is a good idea to review some of the most commonly encountered physics principles and formulae before taking the MCAT.
MCAT Physics Equations: Key Foundings
- You need a solid physics knowledge to do well on the Chemical and Physical Foundations of Biological Systems.
- There’s a number of physics equations you should know.
- It’s not enough only to know the equations. You should also understand, and know how to apply them.
The good news is that the physics equations needed for the MCAT are the ones you are familiar with from your introductory physics class.
Additionally, many questions will provide you with the equations needed to solve the problem - you just need to ensure you can apply knowledge as well as simply memorize equations.
The more comfortable you are with these physics equations, the less likely you will be to freeze - but rather answer the problem quickly and efficiently.
The writers of the MCAT look at physics and how it relates to living systems. Therefore, they broke the most commonly found physics equations down into the following categories :
The first set of equations are from classical, or "Newtonian", physics. They deal with objects, their movement, forces on them, energy, and state of equilibrium. The causes of motion and conversion of energy in living systems are the underlying subject of these equations.
- Average Speed: v = d/t
- Average Velocity: v̅ = Δx/Δt
- Average Acceleration: a̅ = Δv̅/Δt
Translational motion at constant acceleration:
- x - x0 = v0t + ½at2
- v - v0 = at
- v2 = v02 + 2a(x - x0) becomes v = √2gh in free fall where v0 = 0
- v̅ = ½(v + v0)
- Newton's Second Law: F = ma
- Gravity: Fg = G(m1m2)/r2
- FN = mg cos θ
- Fincline = mg sin θ
- Friction: Ffr = μkFN ≤ μsFN
- Hooke's Law: F = -kΔx
- Torque: τ = Fl
- Fdirection = Fopposite direction at equilibrium
- τclockwise = τcounter clockwise at equilibrium
- Fdirection = Fopposite direction ± ma at non-equilibrium
- Kinetic energy: K = ½mv2
- Ug = mgh
- Ue = ½kΔx2
Conservation of energy:
- Etotal = EKE + EPE
- PE1 + KE1 = PE2 + KE2
- Work-energy theorem: W = ΔK + ΔU + ΔEi
- Rest mass energy: E = mc2
- W = Fdcosθ
- W = ΔK + ΔU + ΔEi
- P = Fvcosθ
- P = ΔW / Δt
The next section of equations focuses on the importance of fluids for the circulation of blood, gas movement, and gas exchange. In biological systems, this branch of physics is critical for understanding the pulmonary and circulatory systems.
- Density: ρ = m/V
- Buoyant Force: Fbuoyant = ρVg
- Hydrostatic pressure: P = ρgh
- Continuity equation: A•v = constant
Bernoulli’s equation: p + ρgy + ½ρv2 = constant
Electricity and Magnetism
This set of equations is from electrochemistry, electrical circuits, and their elements. These equations cover biological concepts about how electrical energy may be transformed into work or transmitted over a distance.
- Coulomb’s Law: F = k (Q1Q2/r2)
- Electric field due to a point charge: E = k (Q/r2)
- Electric potential energy: U = k (Q1Q2/r)
- Electric potential: V = k (Q/r)
Constant Electric Fields
- F = qE
- V = Ed
- U = qEd
- U = Vq
Related Article: Electrochemistry for the MCAT
Physics is about questioning, studying, probing nature. You probe, and, if you're lucky, you get strange clues." ― Lene Hau, physicist
- Ohm's Law: I = V/R
- Resistivity: ρ = R•A/L
- Reff = R1 + R2 + ... in series
- 1/Reff = 1/R1 + 1/R2 + ... in parallel
- 1/Ceff = 1/C1 + 1/C2 + ... in series
- Ceff = C1 + C2 + ... in parallel
- Force on a charge moving in a magnetic field: F = qvB sin θ
Waves, Sound, and Light
These equations show how light and sound interact with matter in order for an organism to sense the environment or organs to generate images or structural information.
- Wave velocity: v = fλ
- Wave period: T = 1/f
- Beat frequency: f = |f1 - f2|
- Doppler effect: Δf/fs = v/c and Δλ/λs = v/c
- Photon energy: E = hf
- Snell's Law: n1 sin θ1 = n2 sin θ2
- Lens equation: 1/p + 1/q = 1/f
The final section of physics that the MCAT taker needs to know about is that of atoms, nuclear decay, electronic structure, and atomic chemical behavior.
Although there are no specific equations needed for this category, you should be familiar with chemical equations dealing with the atomic nucleus, nuclear radiation, atomic structure, and how atomic radiation predicts an atom’s chemical and physical properties.
Of course, simply knowing the physics equations is not enough.
After all, the AAMC does not design the test solely to measure specific topic knowledge or coursework completed. Rather, they focus on the science and reasoning skills needed for successful medical education.
The MCAT is all about applying basic knowledge of physics to a variety of scenarios. This means that it is critical to understand how each formula should be applied and when.
But if you can learn and employ the physics equations, you will have the tools you need to do well on this section of the MCAT.