A train is moving on a straight track with speed 20 m cdot s^(-1), It is blowing its shistle at the frequency of 1000 Hz. The percentage change in the frequency heard by a person standing near the track as the train passes him is ( speed of sound = 320 m cdot s^(-1)) close to

A train is moving on a straight track with speed 20 m cdot s^(-1), It

1.	A train is moving on a straight track with speed 20 m cdot s^(-1), It is blowing its shistle at the frequency of 1000 Hz. The percentage change in the frequency heard by a person standing near the track as the train passes him is ( speed of sound = 320 m cdot s^(-1)) close to
Answer» `6%` `12%` `18%` `24%` Solution :Velocity of the listener. `v_(0) = 0,` Velocity of the train, `v_(s) = 20 m//s` So, APPARENT frequency when the train moves towards the listener, `n_(2) = V/(v-(-v_(s)))=320/(320+20) xx1000 = 941.2` HZ HENCE, percentage change in the apparent frequency `=(n_(1)-n_(2))/nxx100 = (1066.7-941.2)/1000xx100` `= 12. 55 % approx12 %` The option (B) is correct.