The rigid bar is pinned at A and supported by two aluminum rods, each having a diameter of 1 in. a modulus of elasticity Eal = 10(103) ksi, and yield stress of (sY)al = 40 ksi. If the bar is initially vertical, determine the angle of tilt of the bar when the 20-kip load is applied.

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