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JEE Mains 28-July-2022 Shift 1 Solved Paper
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© examsnet.com
Question : 57
Total: 90
The frequency of echo will be _______
Hz
if the train blowing a whistle of frequency
320
Hz
is moving with a velocity of
36
km
∕
h
towards a hill from which an echo is heard by the train driver. Velocity of sound in air is
330
m
∕
s
.
[28-Jul-2022-Shift-1]
Your Answer:
Validate
Solution:
The hill will be a secondary source
f
1
=
frequency of the car w.r.t. the hill
f
1
=
(
v
v
−
v
s
)
f
=
(
330
320
)
×
320
=
330
Hz
f
2
=
Frequency of the sound reflected by hill w.r.t. the car (echo)
f
2
=
(
v
+
v
0
v
)
f
1
=
(
330
+
10
)
330
×
330
=
340
Hz
© examsnet.com
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