When a mass of a cart is 10 kg, and an applied force is 5 N, The acceleration of the cart is 5.0 m/s2
2.0 m/s2
0.5 m/s2
0.2 m/s2

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

this would be about 43%