It is possible to hear an approaching train before you can see it by listening to the sound wave through the track. If the Young’s modulus is 2.0 x 10¹¹ N/m² and the density of steel is 7.8 x 103 kg/m³, approximately how many times faster is the speed of sound in the track than in air? (vair ≈ 340 m/s.)
a.20
b.5
c.10
d.15
e.25