If the echo (the reflected sound) reaches your ear less than about 0.1 second after the original sound, your brain doesn't separate them, and you're not aware of the echo even though it's there.
If the echo comes from, say, a wall, 0.1 second means you'd have to be about 17 meters away from the wall. If you're closer than that, then the echo reaches you in less than 0.1 second and you're not aware of it.
A. 30 meters . . . No. You hear that echo easily
B. you're standing within range of both sounds . . . No. You hear that echo easily, if you're at least 17 meters from the wall.
C. less than 0.1 second later . . . That's it. The echo is there but your brain doesn't know it.
Electromagnetism causes like-charged objects to repel each other and oppositely charged objects to attract each other. The electromagnetic force binds negative electrons to the positive nuclei in atoms and underlies the interactions between atoms.
<h2>Here are some examples of situations involving balanced forces.
</h2><h2>Hanging objects. The forces on this hanging crate are equal in size but act in opposite directions.</h2><h2>Floating in water. Objects float in water when their weight is balanced by the upthrust from the water.</h2><h2>Standing on the ground.</h2>
