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A train is moving on a straight track with speed 20 {~ms}^{-1}

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A train is moving on a straight track with speed $20 ms^{- 1}$ . It is blowing its whistle 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 close to (speed of sound $= 320 ms^{- 1}$ )
(a) $6%$
(b) $12%$
(c) $18%$
(d) $24%$

Views: 6,052 students

Updated on: Sep 26, 2022

Book:

Arihant Physics JEE Main Chapterwise Solutions (2019-2002) (Arihant)

Exam:

JEE Mains 2015

Found 4 tutors discussing this question

Levi Discussed

A train is moving on a straight track with speed

20 ms^{- 1}

. It is blowing its whistle 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 close to (speed of sound

= 320 ms^{- 1}

)
(a)

6%

(b)

12%

(c)

18%

(d)

24%

9 mins ago

Discuss this question LIVE

9 mins ago

Text solutionVerified

Exp. (b)
Apparent frequency heard by the person before crossing the train.

f_{1} = (\frac{c}{c - v _{s}}) f_{0} = (\frac{320}{320 - 20}) 1000

Similarly, apparent frequency heard, after crossing the trains

f_{2} = (\frac{c}{c + v _{s}}) f_{0} = (\frac{320}{320 + 20}) 1000

Δ f = f_{1} - f_{2} = (\frac{2 c v _{s}}{c ^{2} - v _{s}^{2}}) f_{0}

\frac{Δ f}{f _{0}} \times 100 = (\frac{2 c v _{s}}{c ^{2} - v _{s}^{2}}) \times 100

= \frac{2 \times 320 \times 20}{300 \times 340} \times 100

= \frac{2 \times 32 \times 20}{3 \times 34}

= 12.54% = 12%

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Question Text	A train is moving on a straight track with speed $20 ms^{- 1}$ . It is blowing its whistle 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 close to (speed of sound $= 320 ms^{- 1}$ ) (a) $6%$ (b) $12%$ (c) $18%$ (d) $24%$
Updated On	Sep 26, 2022
Topic	Waves
Subject	Physics
Class	Class 11
Answer Type	Text solution:1 Video solution: 3
Upvotes	264
Avg. Video Duration	10 min

Text solutionVerified

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A train is moving on a straight track with speed 20 ms−1. It is blowing its whistle 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 close to (speed of sound =320 ms−1 )(a) 6%(b) 12%(c) 18%(d) 24%

Text solutionVerified

Filo tutor solutions (3)

Questions from JEE Mains 2015 - PYQs

Practice questions from Arihant Physics JEE Main Chapterwise Solutions (2019-2002) (Arihant)

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