The lowest frequency in the audible range is 20 Hz. For the steps and strategies involved in solving a similar problem, you may view a Video Tutor Solution. Part A What is the length of the shortest open-open tube needed to produce this frequency

the closer the planet is to the sun, the larger the gravity

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