An observer standing at station observes frequency 219 Hz when a train approaches and 184 Hz when train goes away from him. If velocity of

Q: An observer standing at station observes frequency $219 Hz$ when a train approaches and $184 Hz$ when train goes away from him. If velocity of sound in air is $340\, m/s$, then velocity of train and actual frequency of whistle will be

c (c) When train is approaching frequency heard by the observer is ${n_a} = n\,\left( {\frac{v}{{v - {v_S}}}} \right)$ $⇒$ $219 = n\,\left( {\frac{{340}}{{340 - {v_S}}}} \right)$ …$(i)$ when train is receding (goes away), frequency heard by the observer is ${n_r} = n\,\left( {\frac{v}{{v + {v_s}}}} \right)$ $⇒$ $184 = n\left( {\frac{{340}}{{340 + {v_s}}}} \right)$ …$(ii)$ On solving equation $(i)$ and $(ii)$ we get $n = 200Hz$ and ${v_S} = 29.5m/s.$

SECTION - A [PHYSICS - MCQ]

GSEB - English Medium

An observer standing at station observes frequency $219 Hz$ when a train approaches and $184 Hz$ when train goes away from him. If velocity of sound in air is $340\, m/s$, then velocity of train and actual frequency of whistle will be

A$15.5\,m{s^{ - 1}},\;200\,Hz$
B$19.5\,m{s^{ - 1}},\;205\,Hz$
C$29.5\,m{s^{ - 1}},\;200\,Hz$
D$32.5\,m{s^{ - 1}},\;205\,Hz$

Diffcult

STD 11 Science
NEET
STD 11 - 14. waves and sound
Physics

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