A2 Daily A Level Physics question
In a lab to determine the Young modulus of a metal wire by adding masses and measuring its extension, you want to reduce the percentage uncertainty in the extension reading without changing the measuring scale or the mass steps. Which change to the setup is best?
Answer
The correct answer is C.
Correct: C — Use a longer, thinner steel wire so the extension for each added mass is larger and easier to read. A Short and thick reduces extension for a given load, making percentage uncertainty in the reading larger. B Rubber is not reliably linear in this context and shows hysteresis, so a big stretch does not give a valid modulus. C Longer length and smaller cross-sectional area increase extension for the same load, improving resolution without changing the instrument. D Two wires in parallel share the load and reduce extension, which worsens percentage uncertainty.