A train moves at a constant speed of 26.0 m/s toward the intersection shown in F

Question

A train moves at a constant speed of 26.0 m/s toward the intersection shown in Figure b. A car is stopped near the crossing, 30.0 m from the tracks. The train's horn emits a frequency of 520 Hz when the train is 40.0 m from the intersection.

If the train emits this sound continuously and the car is stationary at this position long before the train arrives until long after it leaves, what range of frequencies do passengers in the car hear?

I know that intensity here has to be on the thresshold of hearing, with I=1 x 10e-12 . but I don't know how to get the frequency form this. HELP!!!!

Explanation / Answer

Apply the Doppler effect

   (f' = f(v/vpm vs))   

Use the plus as the train is moving away and the minus when the train is moving toward

I will assume the speed of sound in air to be 343 m/s since you didn't state otherwise

f' = 520(343/(343 - 26)

f' = 562.6 Hz

and

f' = (520)(343/(343 + 26)

f' = 483.4 Hz

So the range is between 562.6Hz and 483.4 Hz

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.