A rightward-moving skateboarder slows down, decreasing its speed by 0.50 m/s each second.
Now select the acceleration vectors that corresponds to this
motion.
Red arrows: Velocity Blue arrows: Acceleration
.
Tap below to select an Acceleration vector diagram.
A:
D:
B.-
E
C:
F
G.
No acceleration

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