15 A boat travels 12.0m while it reduces its velocity from 9.5 m/s to 5.5 m/s. What is the magnitude of the boat's acceleration while it travels the 12.0m?

frequency or wavelenth of em radiation in a vacuum

i don't understand. explain it clearly

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