Question

Two cars moving in opposite directions approach each other with speed of $22m/s$ and $16.5m/s$ respectively. The driver of the first car blows a horn having a frequency $400Hz$. The frequency heard by the driver of the second car is (Take velocity of sound $340m/s$)

• A. $448Hz$
• B. $350Hz$
• C. $361Hz$
• D. $411Hz$

Answer 1

The correct option is A $448Hz$

Given: $f_1=400Hz$
$V_s=340m/s$
when both source and observer are moving towards each other
Let $V_1$ be the velocity of $1^{st}$ driver and $V_2$ be the velocity of $2^{nd}$
Frequency heard by driver of second car, $f_2=\left(\frac{V_s+V_2}{V_s-V_1}\right)f_1$
$=\frac{340+16.5}{340-22}\times 400=\frac{356.5}{318}\times 400$
$\cong 448Hz$