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.
Answer:
Average velocity (v) of an object is equal to its final velocity (v) plus initial velocity (u), divided by two.
v¯¯¯=(v+u)2
Where:
v¯¯¯ = average velocity
v = final velocity
u = initial velocity
The average velocity calculator solves for the average velocity using the same method as finding the average of any two numbers. The sum of the initial and final velocity is divided by 2 to find the average. The average velocity calculator uses the formula that shows the average velocity (v) equals the sum of the final velocity (v) and the initial velocity (u), divided by 2.
Explanation:
An educated guess about something. (What might happen in the future)
Answer:
False
Explanation:
This proposition is false because by example the sun exerts a force over the earth and them are not in contact