Chapter 6, Problem 42A

Why does a sharp knife cut better than a dull knife?

To determine

The reason that a sharp knife cut better than a dull knife.

Answer to Problem 42A

Because of less area of contact in case of sharp knife.

Explanation of Solution

Introduction:

The pressure exerted by the force $F$ is given by,

  $P=\frac{F}{A}$

Where, $A=$ area of contact

Since, the force is same for both the cases, the pressure exerted by the knife will be inversely proportional to the area of contact.

Now, the dull knife has more area of contact as compared to the sharp knife. Hence, sharp knife will exert more pressure for the same applied force as compared to the dull knife.

Conclusion:

Due to less area of contact in case of sharp knife, it exerts more pressure as compared to the dull knife. Hence, the sharp knife is better than a dull knife.