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Unit 5: Torque and Rotational Dynamics

6 dot points across 6 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

How are the linear motion of a point on a rotating object and the angular motion of the object related?

Topic 5.2 Connecting Linear and Rotational Motion: relate linear and angular quantities for a point on a rotating rigid body through v = r*omega and a = r*alpha.
A focused answer to AP Physics 1 Topic 5.2, covering the relationships between linear and angular quantities for a rotating rigid body, arc length s = r*theta, tangential speed v = r*omega, tangential acceleration a = r*alpha, and the role of radius, with full worked examples.
9 min answer →

How does the net torque on a rigid body determine its angular acceleration, and how does rotational inertia mediate that relationship?

Topic 5.6 Newton's Second Law in Rotational Form: relate the net torque on a rigid body to its angular acceleration and rotational inertia through tau_net = I*alpha.
A focused answer to AP Physics 1 Topic 5.6, covering the rotational form of Newton's second law tau_net = I*alpha, its parallel with F_net = ma, how net torque produces angular acceleration mediated by rotational inertia, and solving rotational dynamics problems, with full worked examples.
10 min answer →

What does it mean for an object to be in rotational equilibrium, and how is Newton's first law extended to rotation?

Topic 5.5 Rotational Equilibrium and Newton's First Law in Rotational Form: apply the condition of zero net torque for rotational equilibrium, alongside zero net force, to analyze balanced rigid bodies.
A focused answer to AP Physics 1 Topic 5.5, covering rotational equilibrium, the condition of zero net torque, the rotational form of Newton's first law, the two equilibrium conditions for a rigid body, and solving balanced-beam and ladder problems, with full worked examples.
11 min answer →

What determines how hard it is to change an object's rotation, and how does the distribution of mass affect rotational inertia?

Topic 5.4 Rotational Inertia: define rotational inertia as an object's resistance to angular acceleration, and reason about how mass and its distribution from the axis determine it.
A focused answer to AP Physics 1 Topic 5.4, covering rotational inertia (moment of inertia) as the rotational analogue of mass, how it depends on mass and its distance from the axis, the point-mass result I = mr squared, and how distributing mass farther out increases it, with full worked examples.
10 min answer →

How do we describe rotational motion using angular position, velocity and acceleration, and how do the rotational kinematic equations work?

Topic 5.1 Rotational Kinematics: describe rotational motion using angular displacement, angular velocity and angular acceleration, and apply the rotational kinematic equations for constant angular acceleration.
A focused answer to AP Physics 1 Topic 5.1, covering angular displacement, angular velocity and angular acceleration, their units in radians, the rotational kinematic equations for constant angular acceleration, and the parallels with linear kinematics, with full worked examples.
10 min answer →

What is torque, how does it depend on force and lever arm, and why does it cause rotation?

Topic 5.3 Torque: calculate the torque produced by a force as tau = rF sin(theta), and identify the lever arm and the sense of rotation.
A focused answer to AP Physics 1 Topic 5.3, covering torque as the rotational effect of a force, the formula tau = rF sin(theta), the lever arm, the sense of rotation, and why where and how a force is applied matters, with full worked examples.
10 min answer →