Given an incompressible 2d flow with x and z velocity given by u= alpha*x and w= beta* z
a) how are alpha and beta related?
b) if the initial positions (t=0) are given by x and z what are the fluid positions x, z in terms of x, z,t?
c) sketch the x, z fluid element trajectory d) express the velocity field in lagrangian coordinates.

their crystal patterns have been disrupted by stress

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