Question

why does a sharp knife cut objects more effectively than a blunt one?

Answer 1

A sharp knife has an area of application of force lesser than a blunt knife.

We know that

$Pressure=\frac{Force}{Area of application of force}$

So the knife whose area of application of force  is less will exert a larger force than the one with area of application of force big even when same amount of force is used for both.

So the sharp knife having area of application of force less will exert a larger force than the blunt knife.

Hope this helps : )

Answer 2

$\huge\texttt{Answer;}$

Pressure is inversely proportional to area. Sharp knife has a small area of contact than the blunt knife. Thus, a force will exert more pressure while using a sharp knife than while using a blunt knife.