Atennis ball is hit at an angle of 20° to the horizontal with the velocity of 20 m/s. what is its velocity in the y direction? a-7.2 m/s b-19.7 m/s c-6.8 s d- 0.9 degrees

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