The weight of an object is the product of its mass, m, and the acceleration of gravity, g (where g=9.8 m/s2). if an
object’s mass is m=10. kg, what is its weight?
express the weight to two significant figures and include the appropriate units.

truck y has a greater velocity than truck x.

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