A train moves towards a stationary observer with speed 34 m/s. The train sounds a whistle and its frequency registered by the observer is f1. If the train's speed is reduced to 17 m/s, the frequency registered is f2. If the speed of sound is 340 m/s, then the ratio f1/ f2 is

Question

A train moves towards a stationary observer with speed 34 m/s. The train sounds a whistle and its frequency registered by the observer is f1. If the train's speed is reduced to 17 m/s, the frequency registered is f2. If the speed of sound is 340 m/s, then the ratio f1/ f2 is (A) 18/19 (B) 1/2 (C) 2 (D) 19/18

Tardigrade Admin · Accepted Answer

f1=f ((v/v-vs)) f1=f ((340/340-34))= f((340/306)) and f2=f ((340/340-17))= f((340/323)) ∴ (f1/f2)=(323/306)= (19/18)

Q. A train moves towards a stationary observer with speed 34 m/s. The train sounds a whistle and its frequency registered by the observer is $f_{1}$ . If the train's speed is reduced to 17 m/s, the frequency registered is $f_{2}$ . If the speed of sound is 340 m/s, then the ratio $f_{1} / f_{2}$ is

18/19

1/2

2

19/18

$f_{1} = f (\frac{v}{v - v _{s}})$
$f_{1} = f (\frac{340}{340 - 34}) = f (\frac{340}{306})$
and $f_{2} = f (\frac{340}{340 - 17}) = f (\frac{340}{323})$
$∴ \frac{f _{1}}{f _{2}} = \frac{323}{306} = \frac{19}{18}$

Q. A train moves towards a stationary observer with speed 34 m/s. The train sounds a whistle and its frequency registered by the observer is f1​. If the train's speed is reduced to 17 m/s, the frequency registered is f2​. If the speed of sound is 340 m/s, then the ratio f1​/f2​ is

18/19

1/2

2

19/18

f1​=f(v−vs​v​) f1​=f(340−34340​)=f(306340​) and f2​=f(340−17340​)=f(323340​) ∴f2​f1​​=306323​=1819​

Q. A train moves towards a stationary observer with speed 34 m/s. The train sounds a whistle and its frequency registered by the observer is $f_{1}$ . If the train's speed is reduced to 17 m/s, the frequency registered is $f_{2}$ . If the speed of sound is 340 m/s, then the ratio $f_{1} / f_{2}$ is

$f_{1} = f (\frac{v}{v - v _{s}})$
$f_{1} = f (\frac{340}{340 - 34}) = f (\frac{340}{306})$
and $f_{2} = f (\frac{340}{340 - 17}) = f (\frac{340}{323})$
$∴ \frac{f _{1}}{f _{2}} = \frac{323}{306} = \frac{19}{18}$