Q

# Confused! kindly explain, - Oscillations and Waves - JEE Main-4

A block is suspended from the ceiling of an elevator through a string having a linear mass density of $19.2\times 10^{-3}$ kg/m. Find the speed of wave if the elevator goes upward with 2m/s2

• Option 1)

50 m/s

• Option 2)

5 m/s

• Option 3)

10 m/s

• Option 4)

100 m/s

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T = m(g + a) = 4 (10 + 2 ) = 48 N

$v = \sqrt \frac{T}{m} = \sqrt \frac{48}{19.2 X 10 ^{-3}} = 50 m/s$

Speed of wave on string -

$v= \sqrt{\frac{T}{\mu }}$

- wherein

$T=$ Tension in the string

$\mu =$ linear mass density

Option 1)

50 m/s

This is correct.

Option 2)

5 m/s

This is incorrect.

Option 3)

10 m/s

This is incorrect.

Option 4)

100 m/s

This is incorrect.

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