A knife blade is a wedge, which is a type of simple machine. The blade acts as a wedge by concentrating and directing force over a thin, sharp edge, enabling it to separate or cut materials more easily than a straight blade would. Key points:

• Wedge definition: A wedge is essentially two inclined planes back-to-back, forming a sharp edge that can split or cut objects.
• How it works: Applying force on the knife drives the wedge into the material, increasing pressure along the contact line and causing separation along a fault line.
• Common examples: Knife blades, axe blades, chisels, and the cutting edges of scissors are all wedge-type simple machines.

If you’d like, I can show a quick comparison between wedges and other simple machines (lever, incline plane, pulley, screw, wheel and axle, wedge) to reinforce how the knife blade fits into the wedge category.