A2 Daily A Level Physics question

In a Young modulus practical, a steel wire of length 2.0 m and diameter 1.0 mm extends by 0.50 mm when an extra 10 N load is added. A second steel wire of the same length but diameter 0.50 mm is tested with the same additional 10 N. Assuming both remain elastic and at the same temperature, what extension would you expect for the thinner wire, and why?

1. A 2.0 mm, because halving the diameter quarters the cross-sectional area, so the extension is four times larger for the same load. (correct)
2. B 1.0 mm, because extension is inversely proportional to diameter, so halving the diameter doubles the extension.
3. C 0.50 mm, because for a given material and length the extension depends only on the added load.
4. D 0.125 mm, because the smaller diameter makes the wire stiffer so the extension is reduced by a factor of four.