A doorknob is a simple machine consisting of a wheel attached to a shaft, which is used to turn a door open or closed. The wheel and axle are connected at the center of the knob, and when the knob is turned, the wheel rotates around the axle, causing the door to turn.
The doorknob is a very simple machine, but it is a very effective way to open and close doors. It is also a very versatile machine, as it can be used on doors of all different sizes and weights.
