Question

why knife have sharp edges???

Answer 1

Knife have sharp edges to reduce area as if area is small then force exerted on it would be high

Answer 2

knife has sharp edges so that it is able to cut the things easily. as sharp edges result in less area, this more pressure gets applied and hence we are easily able to cut with a sharp knife. we all must have observed that it's difficult to cut with a blunt knife.. as it's area increases less pressure is applied.