A sharp knife cuts better than a dull one because the sharp edge:

A SHARP knife cuts better because its thin edge CONCENTRATES the force over a SMALLER AREA, increasing the PRESSURE. ASVAB Mechanical Comprehension tests pressure (PRESSURE = FORCE ÷ AREA). The same force applied over a smaller area produces greater pressure, allowing the blade to cut. A dull knife spreads the force over a larger area (lower pressure), so it cuts poorly. This is also why sharp points and edges (knives, needles, nails) work — small area, high pressure. The force/area/pressure relationship is commonly tested.