Two trains move towards each other with the
same speed. The speed of sound is 340 m/s. If
the height of the tone of the whistle of one of
them heard on the other changes 9/8 times, then
the speed of each train should be
(a) 20 m/s (b) 2 m/s
(c) 200 m/s (d) 2000 m/s
Answers
Answered by
0
Answer:
A)
Explanation:
According to Doppler effect the the pitch of a sound change due the motion of source is given by:
n
ˉ
=n
v−v
s
v−v
0
Here, v
s
and v
0
are the velocity of the sound source and observer and v=330m/s and
n
ˉ
/n=9/8. Lets assume the velocity of both the the trains are
v
ˉ
. Using the above formula:
n
ˉ
/n=9/8=
v−
v
ˉ
v−(−
v
ˉ
)
. The negative sign used for the opposite direction movement of the trains. Using all the known values we can get the velocity of the trains are 20m/s
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