If a ball is kicked horizontally off of a building at 8.0 m/s, what is the horizontal velocity (vx) after 3 seconds?

if the person is shown to have +90n, then ans is -10n.

if the person is shown to have -90n, then ans is +10n.

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