A crate of mass 100 kg is being pushed in a straight line across a horizontal floor at a constant speed of 4.0 m/s.
The coefficient of kinetic friction between the crate and
the floor is 0.3. Find the net force on the crate.

A. 0 N
B. 300 N
C. 400 N
D. 1200 N

0.11 m/s and 0.28 m/s should be correct

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