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Why does a knife have a sharp edge or a needle has a sharp tip ? |
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Answer» For a given force, the pressure over which the force is exerted depends inversely on the area of contact; smaller the area, greater the pressure. For instance, a force applied to an area of 1 mm2 applies a pressure that is 100 times as great as the same force applied to an area of 1 cm2 . The edge of a knife or the tip of a needle has a small area of contact. That is why a sharp needle is able to puncture the skin when a small force is exerted, but applying the same force with a finger does not. |
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