A person with his ear to the ground, sees a huge stone strikethe concrete pavement. A moment later two sounds are heard from theimpact: one travels n the air and the other in the concrete, andthey are 2.2 s apart. How far away did the impact occur?

it's when something is going so fast it makes a loud noise, breaking the sound barrier, for example: a jet makes a loud noise, not only cause of the jet but because they reached a point where they went so fast that you can year the noise from various parts, kinda like a police car, lets say the car was going   so fast that you hear the siren of the cop car right next to you, but the car is probably a mile a way, it's cos the siren was next to you a few seconds if you understand me

the answer to this is proletariats.

hope this : )