Question

Why do all cutting instrument have sharp edges give reason with example?

Answer 1

They have sharp edges because sharp objects have less area of contact which makes the force applied comparatively less than an instrument with blunt edge.This makes it easier to cut through objects.
Example-A knife has a sharp edge and is easy to cut. A blunt one has more area of contact and more pressure is required and it is difficult to cut through.

Hope this helps!