After walking across a carpeted floor in socks, jim brings his finger near a metal doorknob and receives a shock. what does that demonstrate

electric forces can act at a distance.

When Jim walked across the carpeted floor, his body gained electrons from the carpet. The presence of these electrons generated a force between his finger and the doorknob. Since he did not need to actually touch the doorknob for the electrons to be pulled from his finger, this demonstrates that electric forces can act at a distance.

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