Question
Physics Question on Waves
A police car moving at 22 m/s chases a motorcyclist. The police man sounds his hom at 176 Hz, while both of them move towards a stationary siren of frequency 165 Hz. Calculate the speed of the motorcycle, if it is given that the motorcyclist does not observe any beats (speed of sound = 330 m/s).
A
33 m/s
B
22 m/s
C
Zero
D
11 m/s
Answer
22 m/s
Explanation
Solution
The motorcyclist observes no beats. So, the apparent frequency observed by him from the two sources must be equal.
\hspace20mm f_1=f_2
\therefore\hspace10mm 176 \bigg(\frac{330-v}{330-22}\bigg)=165\bigg(\frac{330+v}{330}\bigg)
Solving this equation, we get v = 22m/s