Astronauts who spend long periods in outer space could be adversely affected by weightlessness. one way to simulate gravity is to shape the spaceship like a cylindrical shell that rotates, with the astronauts walking on the inside surface. explain how this simulates gravity. consider (a) how objects fall, (b) the force we feel on our feet, (c) and other aspects of gravity you can think of

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