Some machines, like the lever, generate a large mechanical advantage. Other machines, like a bicycle, actually have a mechanical advantage lower than 1. Does this mean that the machine is “useless” or not working? Explain your reasoning.

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

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