Powerful Pulleys
Students continue to explore the story of building a pyramid, learning about the simple machine called a pulley. They learn how a pulley can be used to change the direction of applied forces and move/lift extremely heavy objects, and the powerful mechanical advantages of using a multiple-pulley system. Students perform a simple demonstration to see the mechanical advantage of using a pulley, and they identify modern day engineering applications of pulleys. In a hands-on activity, they see how a pulley can change the direction of a force, the difference between fixed and movable pulleys, and the mechanical advantage gained with multiple / combined pulleys. They also learn the many ways engineers use pulleys for everyday purposes.
Figure 1. Notice the pulleys used by this by this crane — an example of how a modern device uses simple machines to perform complex tasks.Copyright NASA, <http://heawww.gsfc.nasa.gov>.
Engineers are experts at exploiting the advantages of simple machines in all sorts of real-world applications that benefit society. They incorporate the mechanical advantage of pulleys into their design of many modern-day structures, machines, products and tools, such as cranes, elevators, flagpoles, zip lines, motors, bicycle rings/chains, clothes lines, water well bucket/rope, rock climbing devices, window blinds and sail/fishing boats. Using multiple pulleys in conjunction with motors and electronics, engineers create complex modern devices that perform much work for very little power.
After this lesson, students should be able to:
- Demonstrate how pulleys are used.
- Explain how pulleys could have been used by engineers in ancient times to do work.
- Identify modern applications in which engineers use pulleys.