Joe, standing near a straight road, records the sound of the horn of a car trave

Question

Joe, standing near a straight road, records the sound of the horn of a car traveling at a constant speed. The recorded frequency as a function of the car s position along the road for trials at different car speeds is accurately graphed below. Equal to The speed in trial T is?.. that in other trials. Greater Than The distance of Joe from the path in Q is ..... In S. Equal to The speed in trial S is ..... to that in Q. Less than The speed in trial S is ..... that in R. Equal to When the car is far away, the average of the frequencies Less than The speed in trial U is ..... that in other trials. Consider the average of 1/(1+x) and 1/((1-x). Is it equal to, greater than or smaller than 1? Using the data on the figure, calculate the speed of the car in trial S. Use 340 m/s for the speed of sound.

Explanation / Answer

using doppler effect,
observed frequency f is given as
f=(c+vr)*f0/(c+vs)

where c=speed of the wave in the given medium=343 m/s(speed of sound in air)
vr=speed of the receiver, positive if it is moving towards the source=0 (as the person recording the frequency is staying constant)

vs=speed of the source, positive if it is moving away from the receiver

so using vr=0 and c=343, we get

f=343*f0/(343+vr)

where we have to determine vr from the data provided about recorded frequency f.

so when the car is moving towards Joe, the frequency will be greater than f0 and when it is moving away from joe, it will be lesser than f0.

f0 will be the frequency , when distance=0

when the car is approaching, greater the speed of the car, vr will be that negative, hence the denominator in the expression for f will be lesser and f will be higher.

so when we record a high frequency, it will mean that the speed is also high.

a)
as frequency at T is maximum, speed is also maximum.
hence speed in trial T is greater than that in other trials.

b)distance of joe from the path in Q is greater than in S.

c)speed in trial S is greater than that in Q.

d)speed in trial S is lesser than that in Q.

e) when the car is far away, the averaage of frequencies is equal to the frequency at rest.

f) speed in trial U is less than that in other trials.

Related Questions

Navigate

• Browse (All)
• Browse J
• Subjects

---

---

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