Mechanical systems come in many shapes and forms, and they have various definitions. Before we can start making machines, we need to know what we’re talking about:
• A mechanism is an assembly of moving parts.
• A machine is any device that helps you do work, from a hammer to a bicycle. A hammer is a machine because it makes your arm longer, so you can do more work.
In this book, we use the mechanical definition of work:
Work = Force × Distance
Force (F) equals mass (m) times acceleration (a), and is written as F = ma (also known as Newton’s second law).
For example, imagine that you’re stomping on a bunch of grapes to make wine. The force the grapes feel when you stand still is equal to your weight, ...