How does the air on a hot day compare with the air on a cold day? Question 5 options: On a hot day, air molecules have more energy. On a cold day, air molecules move faster. On a hot day, the air contains more nitrogen. On a cold day, air molecules don't move at all.

mass and volume are the answers you are looking for

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