# Moments, torque, and angular momentum

Contents

Everything you've learned about motion, forces, energy, and momentum can be reused to analyze rotating objects. There are some differences, though. Here, you'll learn about rotational motion, moments, torque, and angular momentum.

## Rotational kinematics

Learn what angular displacement, angular velocity, and angular acceleration mean, as well as the relationship between them.

14:10

Angular motion variables

In this video David explains the meaning of angular displacement, angular velocity, and angular acceleration.

14:36

Relating angular and regular motion variables

In this video David shows how to relate the angular displacement to the arc length, angular velocity to the speed, and angular acceleration to the tangential acceleration.

9:24

Relationship between angular velocity and speed

How angular velocity relates to speed

14:51

Rotational kinematic formulas

In this video David explains the rotational kinematic formulas and does a couple sample problems using them.

## Torque, moments, and angular momentum

Until this tutorial, we have been completely ignoring that things rotate. In this tutorial, we'll explore why they rotate and how they do it. It will leave your head spinning (no, it won't, but seemed like a fun thing to say given the subject matter).

9:24

Introduction to torque

An introduction to torque

14:14

Moments

Introduction to moments

13:50

Moments (part 2)

2 more moment problems.

11:54

Finding torque for angled forces

In this video David explains how to determine the torque exerted by a non perpendicular force.

13:56

Rotational version of Newton's second law

In this video David explains moment of inertia and the rotational version of Newton's second law and shows how to solve an example problem.

14:59

More on moment of inertia

In this video David explains more about what moment of inertia means, as well as giving the moments of inertia for commonly shaped objects.

14:03

Rotational kinetic energy

In this video David explains what rotational kinetic energy is and how to calculate it.

15:00

Rolling without slipping problems

In this video David explains how to solve problems where an object rolls without slipping.

11:19

Angular momentum

5:56

Constant angular momentum when no net torque

Just like how linear momentum is constant when there's no net force, angular momentum is constant where there's no net torque

9:40

Angular momentum of an extended object

In this video David derives and shows how to use the formula for the angular momentum of an extended object.

14:54

Ball hits rod angular momentum example

In this video David explains how a mass can have angular momentum even if it is traveling along a straight line. Then David shows how to solve the conservation of angular momentum problem where a ball hits a rod which can rotate.

10:00

Cross product and torque

The cross product and the direction of torque