B. the mass of the building attracts you upward slightly
Answer:
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Answer:
is the distance from the obstacle of reflection.
wavelength 
Explanation:
Given that:
- frequency of sound,

- time taken for the echo to be heard,

- speed of sound,

We know,

<em>During an echo the sound travels the same distance back and forth.</em>


is the distance from the obstacle of reflection.
<u>Now the wavelength of sound waves:</u>



Answer:
Explanation:
Let the velocity of car be v . We shall apply doppler's effect . Here the car is running towards the observer .
f = f₀ x(
)
Here f is apparent frequency f₀ is true frequency , V is velocity of sound and v is velocity of source .
Putting the values
860 = 800 x 340 / (340 - v )
1.075 = 340 / (340 - v )
365.5 - 1.075 v = 340
25.5 = 1.075 v
v = 23.72 m /s