What does the slope of a position vs. time graph represent?

Your question asks what the slope of a Position vs. Time graph represents.

Your answer would be Velocity.

The slope of a Position vs. Time graph would represent the velocity of the object.

If the slope is positive, then the object has a positive velocity ,in which it is going forward.

If the slope is negative, then the object has a negative velocity, which means that it's going the opposite direction, or backwards.

If the slope is at a "horizontal" position, this means that the object is stopped or isn't moving at all.

current and voltage can both be different in different parts of a circuit so it matters where you place the ammeter and voltmete

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