Home / Categories / Odd Little Things / Entry 31
Odd Little Things · entry 31 of 52
A wedge splits material by concentrating a pushing force into a narrow leading edge.
The longer version
A wedge turns a push along its length into sideways force at its edge. Because that edge is narrow, the same push is concentrated over a small area, and the resulting pressure exceeds what the material can hold, so it splits. A thin wedge needs less force than a blunt one but must travel further to open the same gap.
Axes, chisels, nails, knives and teeth are all wedges with angles chosen for the job. The trade-off between sharpness and durability explains why a very thin blade dulls quickly while a stout one survives rough use. Counting intuition helps: spreading one push across a wide front divides it, while narrowing the front multiplies it.
Where this entry sits
Odd Little Things looks at the ordinary objects people touch every day and the small mechanisms and histories hiding inside them. Buttons, zips, pencils, mirrors, stairs, stamps, packaging, and road signs all get their turn. The full list sits on the Odd Little Things page, where every entry is listed in order.
More From Odd Little Things
Eight more entriesKeys work by lifting small pins inside a lock to the exact height that frees the cylinder.
Read 33Safety pins stay closed because the spring in the bend keeps pressure on the clasped head.
Read 34Paper clips hold sheets together through spring tension in their bent loops of wire.
Read 35Staples grip paper because their legs are bent inward after passing through the sheets.
Read 36Adhesive tape sticks because a soft layer flows into surface texture and resists being pulled away.
Read 37Hook and loop fasteners join by catching tiny hooks in a dense field of soft loops.
Read 38A ballpoint pen deposits ink from a tiny rotating ball that rolls the ink onto the page.
Read 39Fountain pens rely on capillary action to draw ink steadily down to the writing nib.
Read