70% Sectional Test — AP Physics C: Mechanics Units 1 Through 5

Advanced Checkpoint Before Rotational Energy and Oscillations

The 70% sectional test is the most demanding checkpoint before full mock simulation. It covers Units 1 through 5 of AP Physics C: Mechanics, adding the full rotational dynamics toolkit — moment of inertia integration, torque analysis, and rotational Newton's second law — to all the translational content tested at the 50% stage. Passing this checkpoint confidently means you are ready to tackle Unit 6 (Energy and Momentum of Rotating Systems) and Unit 7 (Oscillations) before your first full mock exam.

What the 70% Sectional Tests

Rotational Mechanics Integration

Unit 5 is the most calculus-intensive addition at this stage. Questions require deriving moments of inertia from the integral definition I = ∫r² dm for standard shapes including thin rods, discs, and rings. The parallel-axis theorem is applied to shift rotation axes, and rotational Newton's second law τ_net = Iα is combined with translational Newton's second law in pulley and constraint problems.

Cross-Unit Problem Structures

At 70% coverage, AP-style problems routinely combine content across multiple units. A single FRQ might require kinematics (Unit 1) to describe the approach, dynamics (Unit 2) for the force analysis, energy methods (Unit 3) for speed at a given position, and rotational dynamics (Unit 5) for an angular acceleration calculation. Recognising which unit's tools apply at each step is a key advanced skill.

Calculus Throughout

Every part of the 70% sectional demands active calculus: integrating to find moments of inertia, differentiating to find torque from a potential energy function, solving ODEs for rotational motion with variable torque. Passive formula recall is not sufficient.

Skills Tested in the 70% Sectional

• Deriving I for rods, discs, and rings from first-principles integration.
• Applying the parallel-axis theorem after deriving I_cm.
• Setting up and solving τ_net = Iα for systems with multiple torques.
• Combining translational and rotational Newton's second law for constrained systems.
• Integrating angular acceleration to find angular velocity and position functions.

Using 70% Sectional Results to Plan Your Final Preparation

After reviewing your results, identify which of the five units contributed the most errors. If moment of inertia integrals are the primary weakness, focused review of the integration setup (choice of dm, coordinate system, limits) should precede Unit 6 study. If cross-unit problems caused difficulty, practise explicitly labelling which physics principle you are applying at each step of a solution.

1. Check whether your torque calculations correctly use the perpendicular distance from the axis to the line of force.
2. Confirm you can derive I for a uniform rod about its end without referencing a formula sheet.
3. Practise writing out both translational and rotational Newton's second law simultaneously for pulley problems.