Work, Machines, and Energy


We must meet two conditions for work to be done:

  1. The object moves
  2. A force must act on the object in the direction the object moves.

In this lesson we look at the concepts required to do work. Additionally, we look at simple and complex machines and forms of energy.


Work is the movement of an object in a direction. Power is the rate at which work is done.

Work is made easier by machine. There are simple and complex machines. Compound machines are made up of two or more simple machines.

Screw   Crowbar

The number of times a machine multiplies an effort force is its mechanical advantage.

Mechanical efficiency (ME) of a machine compares its work output with its work input.

The formula for mechanical efficiency is:

ME = work output/work input x 100%

Energy is the ability to do work. Energy has many forms.


Complete the Lesson Inquiry. Turn it in.

Compound Machine Design

Create an 8x11 inch poster (drawing) of a compound machine that will demolish houses or to do a chore at home.

The machine will be movable. Use more than two simple machines. The complex machine must be able to be 'reused'.

Write a one-paragraph essay describing the compound and how the simple machines are incorporated.

Scan the picture and attach the essay. Turn the drawing in or e-mail the poster to your teacher or parent.

Done Early...

Find pictures of simple machines and create a collage using PowerPoint. Turn it in!