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 learn that an increase in the number of pulleys decreases the force required to lift an object but increases the amount of string that must be pulled, yet the amount of work done is independent of the number of pulleys.
Set up a double pulley and a single pulley each with a 200 g mass. Pull the string of each from the same vertical height down to the base simultaneously. Observe that the mass of the single pulley moves twice as high as the double pulley with twice the force.
Attach Newton Spring Scales to each and quantitatively discover that the force exerted decreases by a factor of 2 for the double pulley as the amount of string that is pulled increases by the same factor. Prove that the number of pulleys is equivalent to this factor. Students learn that the number of pulleys equals the mechanical advantage and that for either pulley the amount of work done is the same.