This program activity and tutorial demonstrates
the concept of a screw. A screw is
a close relative of the inclined plane. If you take a piece of paper cut to the shape of an inclined
plane and wind it around a cylinder, you will get the form of a screw. This is similar to taking an inclined
plane, in the form of a road or railroad tracks, and winding it around a
A wood screw is turned by a screwdriver or ratchet
and the threads advance the screw into the wood at the same time. The amount of distance the screw goes
into the wood for each turn of the screw is called the pitch. Two examples are given below and in the
The screw with steeper thread (higher pitch)
will take more force and less turns to be turned into the wood.
The screw with less steep thread (lower pitch)
will take less force and more turns to be turned into the wood.
The amount of work done to turn the screw into the wood is
the same in both cases. The simple
machine screw changes the way in which the work is done: the higher pitch
requires more effort and less screw turns, while the lower pitch requires less
effort and more screw turns.