A piece of wire is 40 cm long and has a diameter of 2.0 mm. Its resistance is 0.30 ohms.
Which wire of the same material has a resistance of 0.15 ohms?

do you have a formula possibly

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