In this topic you will learn how tools and machines affect your life.

You can move an object by pushing it or pulling on it. The push or pull needed to make something move is called a force. When you make something move by using a force, you are doing work. Work means to apply a force to make an object move. The object may move a little or a lot. However, the object must move some distance for your effort to be called work.

You need something else to do work besides a pushing or pulling force. You need energy. Energy is the ability to do work or to cause changes in matter. Work cannot be done without energy. Energy is transferred from one thing to another.

A machine is anything that helps you do work or makes work easier. Many machines have lots of parts. Some machines have few parts. A simple machine is a machine with few parts. Many simple machines are called tools. There are six different types of simple machines. They are the lever, the pulley, the wheel and axle, the inclined plane, the screw, and the wedge. Ancient people may have been inspired by animals to invent tools.

A lever is a bar that can turn on a pivot or fixed point, called a fulcrum. There are three kinds of levers: first-class levers, second-class levers, and third-class levers. Levers make it easier for people to lift heavy objects or open things. The object being lifted by a simple machine such as a lever is called the load. A lever doesn't make you stronger: it changes how much force you need to move something. The effort force is the force you put into a simple machine.

A pulley is made up of a rope, belt, or chain wrapped around a wheel with a groove in it. A wheel and axle are made up of a wheel and a bar that passes through the center of the wheel. An inclined plane is a flat, slanted surface. A wedge changes a downward or forward force into a sideways force. Wheels with teeth are gears.

It took people thousands of years to understand how simple machines could make work easier, based on an understanding of forces, work, and energy.