A mechanic pushes a 2.60 ✕ 103-kg car from rest to a speed of v, doing 4,710 J of work in the process. During this time, the car moves 27.0 m. Neglecting friction between car and road, find v and the horizontal force exerted on the car. (a) the speed v m/s (b) the horizontal force exerted on the car (Enter the magnitude.)

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