Question

A knife with a sharp edge is more effective than a blunt knife because:
(A) The pressure increases due to decrease in surface area of contact.
(B) The force increases due to decrease in surface area of contact.
(C) It’s velocity ratio decreases.
(D) It gets blunt due to long use.

Answer 1

Hint: We know that pressure is inversely proportional to the surface area. It means a knife with a shaped edge has more pressure due to the decrease in surface area of contact.

Complete step by step answer
The knife uses pressure to cut anybody and we know that pressure increases with the decrease in surface area of the body.
The pressure is defined as the ratio of force per unit area. It can be expressed as-
\[P = \dfrac{F}{A}\]
It means the pressure is directly proportional to force and it is inversely proportional to the body of the surface area. If the surface area of pressure increases the pressure decreases and vice-versa.
In a sharp-edged knife, the surface area is less as compared to a blunt knife edge. It means we have to apply more pressure in the blunt knife to cut the same body which we can easily cut using the Sharp edge knife.
Therefore, the pressure increases due to the decrease in surface area of contact, and because of this, the knife with a sharp edge is more effective than a blunt knife.

Thus, option A is correct.

Note
The majority confuses option A and option B and tick option B as their response but it is noted that the actual reason for the knife with a sharp edge is more effective than a blunt knife is pressure and not force. We can cut more easily with a Sharp edge knife.