Plan a practical to investigate the ratio heating of various metals using a joule meter to determine the energy input. If no joule meter is available, use an ammeter ,I, a voltmeter ,V, and heat the material for a fixed amount of time ,t, Calculate the energy transferred. Thanks :)

the answer for apex is the lowest

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