A 45-g object accelerates from rest to a final velocity in 6.5 seconds. If the magnitude of the net force acting upon the object is 42.0 N, the final velocity reached by the object is m/s.

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

the maxium height is 34m/s