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.
Hey there mate :)
Even if two persons are given the same work load, the speed of the work done gets different by the energy of those persons.
No one is sure that he/she can complete the work within the time. He may or may not.
Also, the physical characteristics makes the work different. If one person has so much power to work all day, the other person may not have.
Therefore, <em>even if two persons do the same amount of work , they may have different power</em><em>.</em>
This is because of of the heating effect of a current. The glow is a result of current passing through the filament. The current experiences resistance as a result heat is generated. When resistance is at zero, there potential differences is not needed hence temperature generated will be at a constant.
1. No they aren’t because they all belong to different sports and are used differently
