Levers That Lift
Figure 1. A lever, one of the six simple machines.Copyright U.S. Department of Transportation, Federal Highway Administration, http://www.fhwa.dot.gov/environment/fspubs/05232810/page16.htm
Students are introduced to three of the six simple machines used by many engineers: lever, pulley, and wheel-and-axle. In general, engineers use the lever to magnify the force applied to an object, the pulley to lift heavy loads over a vertical path, and the wheel-and-axle to magnify the torque applied to an object. The mechanical advantage of these machines helps determine their ability to make work easier or make work faster.
Simple machines are extremely valuable to engineers since they are used to accomplish extraordinary amounts of work with ease. In particular, engineers can design a simple machine which provides a desired mechanical advantage so that work can be done (more) efficiently and effectively. Even the most complex machines designed by engineers today are a combination of one or more of the six known simple machines. The lever, pulley, and wheel-and-axle can be found in many engineered devices, such as a crowbar, crane, and bicycle.
After this lesson, students should be able to:
- Explain how the lever, pulley, and wheel-and-axle make work easier.
- Identify how the lever, pulley, and wheel-and-axle are used in many familiar engineering systems today.
- Discuss the mechanical advantage of a lever, pulley and wheel-and-axle.