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A wire hangs from a ceiling and is stretched by a weight F attached at its lower end; the ceiling exerts an equal and opposite force F on the wire. Considering any cross section of area A, which statement is correct?

1. The tensile stress at any cross section A of the wire is F/A.
2. The tensile stress at any cross section A of the wire is zero.
3. The tensile stress at any cross section A of the wire is 2F/A.
4. The tension at any cross section A of the wire is 2F.

Correct answer: The tensile stress at any cross section A of the wire is F/A.

Solution

The two equal external forces F and F are what create a tension of magnitude F throughout the wire, so the stress at any cross section is F/A.

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