Question

A police car moving at $22m/s$, chases a motorcyclist. The police man sounds his horn at $176Hz$, while both of them move towards a stationary siren of frequency $165Hz$. Calculate the speed of the motorcycle, if it is given that he does not observes any beats

• A. 33 m/s
• B. 22 m/s
• C. Zero
• D. 11 m/s

Answer 1

Answer: (B)

$n_1=$ Frequency of the police car horn observer heard by motorcyclist
$n_2=$ Frequency of the siren heard by motorcyclist.
$v_2=$ Speed of motor cyclist
$n_1=\frac{330-v}{330-22}\times 176;$
$n_2=\frac{330+v}{330}\times 165$
$\because n_1-n_2=0$
$\Rightarrow v=22m/s$