• # question_answer Two cars are moving towards each other with same speed, if frequency of horn blown by driver of one car and frequency appeared to another driver differ by 4% from the frequency of horn, then find out speed of cars (speed of sound =300 m/s) A)  12 m/s             B)  6.6 m/s C)  4.2 m/s                       D)  5.9 m/s

As       ${{v}^{'}}=1.04\,v$ $=v\left( \frac{300+{{v}_{0}}}{300-{{v}_{0}}} \right)$ $\Rightarrow$            $300+{{v}_{0}}=300\times 1.04-1.04\,{{v}_{0}}$ or         $2.04\,{{v}_{0}}=0.04\times 300$ $\therefore$    ${{v}_{0}}=5.88\,m/s\simeq 5.9\,m/s$