We know that Pressure is inversely proportional to area.
So, smaller area will exert more pressure, thus a sharp knife has small area that comes in contact with the object, so more pressure can be applied on the object. Whereas a blunt knife has more area than a sharp knife and the pressure exerted by the blunt knife will be less as compared to that of a sharp knife.
Therefore it becomes easy to cut objects with a sharp knife than a blunt knife and so the edge of knife kept sharp.
