AP Physics Mechanics: Complete Topic Guide

Mechanics is the foundation of both AP Physics 1 and AP Physics C: Mechanics. Whether you're approaching it algebraically (Physics 1) or with calculus (Physics C), the conceptual framework is the same — what changes is the mathematical treatment and depth of problems expected.

This guide covers every major mechanics topic with AP exam context throughout.

1. Kinematics

Kinematics describes motion without asking why it happens. For AP Physics 1, you'll use the standard constant-acceleration equations. For Physics C, you'll integrate or differentiate position, velocity, and acceleration functions.

Key relationships

• v = dx/dt (Physics C) or Δx = area under v-t graph (Physics 1)
• a = dv/dt (Physics C) or a = slope of v-t graph (Physics 1)
• For constant acceleration: v² = v₀² + 2aΔx

Projectile motion is tested on every AP Physics 1 exam. The key: horizontal and vertical motions are independent. Time of flight connects them.

2. Newton's Laws and Force Analysis

AP Physics places heavy emphasis on applying Newton's laws, not just stating them. Every force problem requires a free body diagram (FBD) — this earns explicit points on the FRQ section.

Common force scenarios

• Atwood machine: Two masses over a pulley. Set up Newton's second law for each mass separately, with consistent sign convention. Tension is the same throughout an ideal (massless) string.
• Inclined plane: Resolve into components parallel and perpendicular to the surface. Normal force is not mg on an incline.
• Connected objects: Treat the system as a whole to find acceleration, then isolate individual objects to find internal forces.

3. Work, Energy, and Power

Energy methods often simplify problems that would require complex force analysis. The work-energy theorem: W_net = ΔKE. Conservation of energy applies when only conservative forces act.

For Physics C, work is W = ∫F·dx — this allows you to handle variable forces, which appear frequently on Physics C: Mechanics FRQs.

4. Momentum and Impulse

Momentum conservation is one of the most consistently tested topics in AP Physics 1. For any collision or explosion problem, identify whether external forces act. If they don't (or the collision is brief), momentum is conserved.

• Elastic collision: KE and momentum both conserved. Rare in practice; common on exams.
• Perfectly inelastic: Objects stick together; only momentum conserved.
• Explosions: Start at rest; total momentum after = 0.

Impulse-momentum theorem: J = FΔt = Δp. Area under a force-time graph = impulse = change in momentum.

5. Rotational Motion (Heavily Tested on Physics C)

Rotational mechanics is an extension of linear mechanics. The analogies are direct: torque (τ) is to force (F) as angular acceleration (α) is to linear acceleration (a), and rotational inertia (I) is to mass (m).

• τ_net = Iα (Newton's second law for rotation)
• L = Iω (angular momentum)
• KE_rot = ½Iω²

Rolling without slipping problems combine linear and rotational mechanics: v_cm = Rω. These appear on almost every Physics C: Mechanics FRQ.

6. Simple Harmonic Motion

SHM appears in both Physics 1 and Physics C. The restoring force is proportional and opposite to displacement: F = −kx (for a spring) or F = −mgx/L (small angle pendulum).

Key quantities: period T = 2π√(m/k) for a spring, T = 2π√(L/g) for a pendulum. Note that period does not depend on amplitude — this is a classic conceptual test point.

For Physics C, SHM is solved using the differential equation d²x/dt² = −ω²x, giving x(t) = A cos(ωt + φ).

For personalised mechanics instruction — including FRQ practice and calculus-based problem solving — our AP Physics C Mechanics online tutoring is structured specifically around the exam curriculum. We also offer AP Physics 1 tutoring online for students taking the algebra-based course.