Kinematics and Dynamics

Chapter 1: Kinematics and Dynamics

3 min read Updated Mar 26, 2026
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1. (1.1) The SI unit of force is:
A. Dimensional analysis: kg × m/s² = N by definition.
2. (1.2) A vector quantity has:
B. Scalars (mass, time, temperature) have only magnitude.
3. (1.3) Two perpendicular vectors of magnitudes 3 and 4 have a resultant magnitude of:
C. Pythagorean theorem applies to perpendicular vectors.
4. (1.3) To subtract vector B from vector A (i.e., compute A - B):
D. A negative vector has the same magnitude but points in the opposite direction.
5. (1.4) Displacement is:
A. A circular path has net displacement of zero regardless of distance traveled.
6. (1.4) Instantaneous velocity is:
B. Speed is the magnitude of velocity; velocity is a vector.
7. (1.5) Under uniform acceleration starting from velocity v₀, velocity at time t is:
C. The first kinematic equation.
8. (1.5) Under uniform acceleration, displacement equals:
D. Integrate v = v₀ + at once to get position.
9. (1.5) The time-independent kinematic equation is:
A. Useful when you have initial and final velocities and acceleration but not time.
10. (1.6) In projectile motion with no air resistance:
B. Separating the motion into independent x- and y-components is the key to solving projectile problems.
11. (1.6) The range of a projectile on level ground is maximized at launch angle:
C. R = v₀² sin(2θ) / g is maximized when sin(2θ) = 1, i.e., 2θ = 90°, so θ = 45°.
12. (1.7) Newton's first law states:
D. Also called the law of inertia.
13. (1.8) Newton's second law states:
A. The net (vector sum of) force causes acceleration; F and a point the same way.
14. (1.8) Doubling the net force on an object (with mass constant):
B. The acceleration is linear in the applied net force.
15. (1.9) Newton's third law says:
C. The action-reaction pair acts on different objects, so they do not cancel on a single body.
16. (1.10) The force of kinetic friction equals:
D. Kinetic friction is usually slightly less than maximum static friction.
17. (1.11) On a frictionless inclined plane of angle θ, a block's acceleration down the slope is:
A. The component of gravity along the incline is mg sin θ; divide by m to get acceleration.
18. (1.12) In uniform circular motion:
B. Speed is constant, but the direction changes; hence nonzero acceleration directed inward.
19. (1.12) The centripetal force needed to keep mass m moving at speed v in a circle of radius r is:
C. Derives from F = ma with aca_{c} = v²/r.
20. (1.13) Newton's law of universal gravitation is:
D. Near the Earth's surface this simplifies to F = mg, with g ≈ GM_Earth / REarthR_{\text{Earth}}² = 9.81 m/s².
21. (1.14) The center of mass of a two-particle system sits:
A. Newton's second law applies cleanly to the center of mass of an extended object or system.
22. (1.15) Momentum is defined as:
B. Conserved in a closed system. Units are kg·m/s.
23. (1.15) The impulse-momentum theorem states:
C. Airbags reduce injury by increasing Δt and therefore reducing the peak force for a given momentum change.
24. (1.16) In a perfectly elastic collision:
D. Ideal billiard-ball collisions approximate elastic. Perfectly inelastic collisions stick together and lose the most KE (momentum is still conserved).

You’re a passenger in a car at a red light. The light turns green and the driver mashes the gas. Your body slams backward into the seat. A few seconds later, they brake hard at the next intersection — now your body lurches forward, the seatbelt catching you across the chest. You didn’t choose to fly forward or backward. Forces and inertia made that decision for you.

Every physical event you’ll ever experience — a baseball arcing through the air, a patient sliding off a hospital bed, blood flowing through your veins, a pencil rolling off a desk — is governed by a small set of rules about how objects move, why they speed up, and what happens when they collide. The MCAT expects you to know these rules cold and apply them to unfamiliar passages in under 90 seconds per question.

This chapter is the foundation of MCAT physics. Kinematics tells you how objects move (position, velocity, acceleration). Dynamics tells you why they move (forces). Together, they account for roughly 25–30% of the physics questions you’ll see on test day. Master this chapter and you’ll have the toolkit to handle everything from projectile motion to elevator problems to car crashes — and almost every other chapter (energy, fluids, waves, circuits, optics) will build on what you learn here.


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