AP Physics 1 ›  Unit 5

Unit 5 Torque & Rotational Dynamics

Everything that spins, pivots, and turns. Six episodes that take rotation from description through Newton's Laws to equilibrium and angular acceleration.

📋 10–15% AP Exam Weighting🕐 ~16–22 Class Periods📺 6 Episodes✅ Progress Check 5
EP.5.1

Rotational Kinematics

Unit 1 revisited — same three kinematic equations, new variables. Angular displacement, velocity, and acceleration describe every spinning object.

Dtheta, omega, alphaomega = omega_0 + alpha*tCCW = positiverad/s, rad/s²
🕐 3–4 daysOpen →
EP.5.2

Connecting Linear and Rotational Motion

The bridge between spinning and moving. Radius r is the multiplier that converts every angular quantity into its linear counterpart at any point on a rigid system.

s = r*thetav = r*omegaa_T = r*alphaRigid system rule
🕐 2–3 daysOpen →
EP.5.3

Torque

Force causes linear acceleration. Torque causes angular acceleration. Where you apply the force and at what angle determines how effectively it rotates a system.

tau = rF sin(theta)Lever armTorque diagramsCCW = positive
🕐 3–4 daysOpen →
EP.5.4

Rotational Inertia

Mass resists linear acceleration. Rotational inertia resists angular acceleration — and it depends on how far that mass sits from the axis, not just how much there is.

I = mr²I_tot = Sum(mr²)Hoop > diskI' = I_cm + Md²
🕐 2–3 daysOpen →
EP.5.5

Rotational Equilibrium

When net torque is zero, angular velocity stays constant. The rotational analog of Newton's First Law — and the key to every balance and seesaw problem.

tau_net = 0Constant omegaStrategic pivot choiceStatic balance
🕐 3–4 daysOpen →
EP.5.6

Newton's Second Law for Rotation

F = ma for spinning systems becomes tau_net = I*alpha. The rotational version of the most powerful law in mechanics — and the season finale of Unit 5.

tau_net = I*alphaalpha = tau/ICombined linear + rotationala = r*alpha
🕐 3–4 daysOpen →
🎓 AP Classroom — Progress Check 5
Covers all six episodes. Equilibrium and tau_net = I*alpha FRQs require full torque diagrams with labeled pivot points and explicit equations.
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