Splitting Forces
A wedge is a simple machine that converts a force applied to its blunt end into forces perpendicular to its inclined surfaces. It is essentially a moving inclined plane, commonly used to separate two objects, split an object, lift an object, or hold an object in place.
The mechanical advantage of a wedge depends on the ratio of its length to its thickness (width). A long, thin wedge has a higher mechanical advantage and is easier to drive into a log than a short, fat wedge.
Practical Applications
Wedges are perhaps the oldest simple machines used by humanity. Early flint hand axes were essentially simple wedges. Today, they are everywhere:
- Cutting Tools: Axes, knives, chisels, and scissors all use a wedge edge to split material apart.
- Fasteners: Nails and pins act as wedges, pushing material aside as they are driven in.
- Stoppers: Doorstops wedge themselves between the floor and the door, utilizing friction to prevent movement.
The Formula
Example Calculation
Consider an axe head (which acts as a wedge) that is $20 , ext{cm}$ long and $4 , ext{cm}$ wide at the blunt end.
- Divide Length by Width: $20 / 4 = 5$.
The ideal mechanical advantage is $5$. If you swing and strike the wood with a force of $1000 , ext{N}$, the wedge exerts a massive outward splitting force of $5000 , ext{N}$ directly onto the wood grain.