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When the sound is produced in an aeroplane moving with a velocity of 200 m/s horazontally its echo is heard after 10\sqrt{5}\;s. If velocity of sound in air is 300 m/s, the elevation of aircraft is 

  • Option 1)

    250 m

  • Option 2)

    250\sqrt{5}\; m

  • Option 3)

    1250 m

  • Option 4)

    2500 m

Answers (1)

best_answer

Time for the echo = 10 \sqrt{5} s  ( i.e. , for sound to travel ABC)

Velocity of the plane = 200 m/s

OC = 200 X 5\sqrt{5} = 2236 m

BC = velocity of sound X 5\sqrt{5}

\RightarrowBC = 300 X 5\sqrt{5} = 3354 m

\therefore OB = \sqrt{BC^{2} - OC^{2}}

OB = 2500 m

The plane is 2500 m above the ground.

 

Effect of Humidity on speed of sound -

With the increase in humidity, the density of air decreases. Now the speed of sound in air will increase.


 

- wherein

Since

v\alpha \frac{1}{\sqrt{\rho }}

\rho = decreases

v= increases

 

 

 


Option 1)

250 m

This is incorrect.

Option 2)

250\sqrt{5}\; m

This is incorrect.

Option 3)

1250 m

This is incorrect.

Option 4)

2500 m

This is correct.
Posted by

divya.saini

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