A steel rod has density and allows sound to travel along its length at

PHYSICS · Single correct · A Level · Physics · Mechanics and materials · Mechanics and materials

Problem

A steel rod has density

7.8\times10^{3}\,\text{kg m}^{-3}

and allows sound to travel along its length at

5.0\times10^{3}\,\text{m s}^{-1}

. After alloying, the density becomes

8.6\times10^{3}\,\text{kg m}^{-3}

and the measured sound speed is

4.8\times10^{3}\,\text{m s}^{-1}

. What is the closest estimate of the percentage change in Young’s modulus due to alloying? (a) Increases by about

5.8\%

(b) Decreases by about

7.8\%

1.6\%

(d) Increases by about

10\%