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Knives, needles and nails are deliberately given sharp or pointed edges. The reason is:
ASharp edges decrease friction completely
BA smaller area increases the force itself
CA smaller area concentrates the same force, producing larger pressure
DSharp edges store more energy
Answer & Solution
Correct answer: C. A smaller area concentrates the same force, producing larger pressure
Since pressure equals force divided by area, reducing the contact area while keeping the applied force the same increases the pressure on the surface. That is why the pointed end of a nail can be driven into wood while the flat head cannot — the same force is concentrated on a much smaller area.
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