Because the blade is sharp so it will easily slide through.
Because your knives are all dull. Sharp knives cut tomatoes quite easily.
Because sharp knives cut better.
Sharp knives are less likely to slip off of the material being cut, and so are considered safer.
so they can cut stuff...
Knives are sharp to cut things and you can win some here http://woobox.com/rdk82y/4y2n8i
Knives and scissors have edges to cut things, but nails do not have sharp edges, they have points to penetrate hard surfaces.
the sharp knives work better because they give u a better cut then blunt ones
To cut things, obviously. However, not all knives have sharp edges. The sharpness of a particular knife depends on how it is used. And sharpness is all relative anyway. In the West, butter knives and spreaders have dull edges. Knives intended to cut meat, such as carving and steak knives, are much sharper. And knives intended to chop vegetables and other fibrous foods are the sharpest of all. Also, not all cutting edges belong to knives. My favorite example is the splayd, a tool of Australian origin that combines a fork, spoon and knife into one implement. The knife edge is on the side of the spoon bowl.
To cut things, obviously. However, not all knives have sharp edges. The sharpness of a particular knife depends on how it is used. And sharpness is all relative anyway. In the West, butter knives and spreaders have dull edges. Knives intended to cut meat, such as carving and steak knives, are much sharper. And knives intended to chop vegetables and other fibrous foods are the sharpest of all. Also, not all cutting edges belong to knives. My favorite example is the splayd, a tool of Australian origin that combines a fork, spoon and knife into one implement. The knife edge is on the side of the spoon bowl.
they will make a ragged cut which will get more infected easily. I think
A sharp knife will cut/slash/chop easier.
The edge of a knife is very thin, often a few molecules thick. The thin edge will then apply very high force per unit of area, splitting the material being cut, separating the molecules of the material being cut.