The Pulley Demonstration System is designed to complement demonstrations of simple machines. From the wheels on a bicycle to the gears in a car, the Pulley Demonstration System helps explain how things work. Students quickly learn that using more pulleys reduces the force required to lift an object, but increases the amount of string that must be pulled. These exercises demonstrate that the amount of work done is independent of the number of pulleys used.
Application 1: Set up a double pulley and single pulley, placing a 200 g mass on each one. Simultaneously pull each pulley’s string from the same vertical height down to the base. Notice that the single pulley’s mass moves twice as high as the double pulley’s with twice the force.
Application 2: Attach Newton Spring Scales to quantitatively demonstrate that the double pulley’s exerted force decreases by a factor of 2, while the amount of pulled string increases by the same factor. From here, students can easily prove that the number of pulleys is equivalent to this factor. Students will learn that the number of pulleys is equal to the mechanical advantage, and that the amount of work done is the same for both pulleys.