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A needle is required for stitching cloth, We use knife for cutting fruit. If the tip of a needle or the edge of a knife becomes blunt, then the needle does not penetrate the cloth and the knife does not cut into the fruit. Why is this so?

Explanation

If the needle becomes blunt or the edge of the knife loses sharpness, we need to put more force while using these. The frictional force also rises and therefore we cannot expect the same work from these equipment. Hence the needle as well as knife will not function the way they are supposed to work.