Question

Why is a sharp knife more effective in cutting fruit than a blunt knife?

Answer 1

1. The effect of a force applied is measured by the pressure it exerts, i.e, higher pressure causes a greater effect of force.
2. $Pressure=\frac{Forceactingnormallyonthesurface\left(Thrust\right)}{Areaofthesurface}=\frac{F}{A}$
3. From the above formula for a certain force, pressure is inversely proportional to the area of the surface.
4. Thus, the effect of force is increased by decreasing the area on which it acts.
5. All cutting instruments, such as knife, blades, axes, picks, etc. are made sharper at the cutting edge.
6. The sharper cutting edge has a smaller area of cross-section. As a result, such instruments exert more pressure and easily penetrate into the given surface/ object.

Hence, A sharp knife is more effective in cutting a fruit than a blunt knife because the area of contact in the case of a sharp knife is lesser than that of a blunt knife.