## Chapter 9: Force

9.5 Mechanical equilibrium An object (or group of objects) is said to be in mechanical equilibrium when the net force on it is zero. You could also describe this in terms of an object’s motion, considering Newton’s second law: an object is Continue Reading

## Chapter 9: Force

9.4: Problem solving steps We’ll follow the same problem-solving steps as with problems dealing with conservation laws, but this time we’ll add an intermediate step between the drawing and the math: Draw a picture. Using your picture, draw a free Continue Reading

## Chapter 9: Forces

9.3 Types of forces In the classical model of physics, we describe many different forces depending on what things are interacting. A few of these forces have a distinct mathematical expression. Weight is the force of gravity of the Earth Continue Reading

## Chapter 9: Force

9.2 Newton’s laws In the late 1600s and early 1700s, Isaac Newton published the Principia Mathematica in which he built upon discoveries of scientists (at the time called “natural philosophers”) before him, laying the foundation of classical mechanics. In the Principia, he described Continue Reading

## Chapter 8: Angular momentum

8.3: Collisions In addition to describing the rotational motion of a single object while its moment of inertia changes, we can also look at what happens when two rotating objects collide. Example 8.2 Two disks are spinning counter-clockwise. One disk Continue Reading

## Chapter 8: Angular momentum

8.2 Conservation of angular momentum Just like linear momentum, if there is no external influence* acting on an object then angular momentum is conserved: A very important result of this describes how a body’s angular speed changes as mass comes Continue Reading

## Chapter 8: Angular momentum

Considering conservation of linear momentum $$\left(\vec{p}\right)$$ allows us to understand many phenomena that we observe, but it is insufficient to describe situations that involve rotation. 8.1 Angular momentum The magnitude of linear momentum is given by or Let’s break this Continue Reading

## Chapter 7: Linear momentum

7.4 Two-dimensional collisions When you are dealing with objects that are not moving along a single axis, you must remember that velocity—and therefore momentum—is a vector. This means that both the $$x$$ and $$y$$ components of momentum are conserved in Continue Reading

## Chapter 7: Linear momentum

7.3 Ballistic pendulum A ballistic pendulum is a device that used to be used to determine the velocity of a bullet; it was invented in 1742 by English mathematician Benjamin Robins for this purpose. A simple version consists of a block of Continue Reading

## Chapter 7: Linear momentum

7.2 Collisions In a collision: Two or more objects strike each other The total external force is either zero or negligible, and therefore momentum is conserved Collisions are categorized by what happens to the total kinetic energy of the system. Continue Reading