Answer:
2125m
Explanation:
Using equation of motion
s = ut + ½at²
For motion under gravity
s = ut + ½gt²
Where u = 400m/s
g = 10m/s²
t = 10 /2 = 5s , this is because it takes double time to hear the sound just like echo
Therefore
s = ut +½gt²
s = 400×5 + ½ ×10× 5²
s = 2000 + 25×5
s = 2000 + 125
s = 2125m
The depth of the hole is 2125m or 2.125km
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