It Is Possible to Hear an Approaching Train Before You $\approx$

question 9

Multiple Choice

It is possible to hear an approaching train before you can see it by listening to the sound wave through the track. If the elastic modulus is 2.0*1011 N/m² and the density of steel is 7.8 *103 kg/m3, approximately how many times faster is the speed of sound in the track than in air? (vair $\approx$ 340 m/s.)

• A)20
• B)5
• C)10
• D)15
• E)25

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