Several companies produce personal water filters that can travel anywhere. Such filters make any water safe to drink by removing bacteria and other contaminants. However, they cannot filter heavy metals and viruses or remove salt. The filters are constructed of sturdy plastic and weigh just two ounces. They can be purchased in stores or online for about $20. Evaluate this design by describing the criteria it does or does not meet.

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