3. A truck moving at 26 m/s passes a police car moving at 35 m/s headed in the o

Question

3. A truck moving at 26 m/s passes a police car moving at 35 m/s headed in the opposite direction. a) If the frequency of the siren relative to the police car is 500 Hz, what is the frequency heard by an observer in the truck as the police car approaches the truck? b) What is the frequency heard by an observer in the truck after the truck passes the police car? c) Assume now that the police car is behind the truck and they are both moving in the same direction. What is the frequency heard by an observer in the truck in this case? Take the speed of sound in air as 343 m/s.

Explanation / Answer

Given,

vt = 26 m/s ; vc = 35 m/s ; f = 500 Hz

a)f' = (vt + vs)/(vs - vc) f

f' = (26 + 343)/(343 - 35) x 500 = 599.03 Hz

Hence, f' = 599.03 Hz

b)f' = (vs - vt)/(vs + vc) f

f'' = (343 - 26)/(343 + 35) x 500 = 419 Hz

Hence, f'' = 419.31 Hz

c)f''' = 599.03 - 419.31 = 179.72 Hz

Hence, f''' = 179.72 Hz

Related Questions

Navigate

• Browse (All)
• Browse 3
• Subjects

---

---

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