Objects on Mars weigh about 38% what they do on Earth. While driving on Earth, a Mars rover moves at a speed of 30 mph. If the rover moves with the same speed on
Mars, would it have more, less, or the same momentum as when on Earth?

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