Lever principle: sometimes one hand holds the front end of the knife against the cutting board, and the hard object forms a fulcrum under the knife, while the other hand presses the handle, and the kitchen knife forms a labor-saving lever, which makes it more labor-saving to cut the hard object.

Momentum theorem: "chopping work" when chopping is needed. When MV=Ft, chopping time is short, and the destructive power to vegetables is inversely proportional to time.

Dynamic load coefficient: Sometimes when the knife is pressed on hard fruits and vegetables, the sudden stiffening and downward pressure are equivalent to twice that of the static pressure channel, that is, K=2.