With a spring dynamometer, the weight of a sandbag is measured at the equator, it is 1N. Do you have to add or remove sand from the bag so that the dynamometer shows 1N at the north pole

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