It is difficult to cut things with a blunt knife because

Pressure is defined as the force applied per unit area (P = F/A) [3]. In the case of a knife, the force applied is distributed over the area of the knife's edge. A sharp knife has a very small surface area at its edge, which results in a higher pressure for a given force, making it easier to penetrate and cut through materials [1]. Conversely, a blunt knife has a larger surface area at the edge. According to the pressure formula, as the area (A) increases for a constant force (F), the resulting pressure (P) decreases. Therefore, it is difficult to cut with a blunt knife because it decreases the pressure exerted for a given force, requiring significantly more effort to achieve the same cutting effect.

Sources

1. [2] Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 6: Pressure, Winds, Storms, and Cyclones > 6.1 Pressure > p. 82
2. [3] Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 6: Pressure, Winds, Storms, and Cyclones > 6.1 Pressure > p. 81
3. [1] Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 6: Pressure, Winds, Storms, and Cyclones > Safety first > p. 83