The echo is heard 2.80 s later, this means this is the time the sound takes to travel to the reflecting object and then back to us. So, during this time, the sound wave has covered the distance L between us and the object twice:

The speed of the sound wave is:

, and since it is moving by uniform motion, we can find the distance covered by the wave using

And we said this corresponds to twice the distance between us and the reflecting object, so:

so, the object is 480 meters away.
<span>Centripetal force acts toward the center of the circle, and inertia keeps the object moving forward.
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It would be D I believe! Depending on the angle of the mirror and distance positioned!
Answer:
12N
Explanation:
when a force is applied to a body but still stays at rest or moves at a constant speed , the frictional force is equal to the force applied