Boron coated with SiC (or Borsic) reinforced aluminum containing aligned 20 vol% fibers is an important high-temperature, lightweight composite material. Estimate the modulus of elasticity perpendicular to the fibers. The modulus of elasticity of the fibers is 55 X 106 psi and the modulus of elasticity of aluminum is 10 X 106 psi.
a. 19 X 106 psi
b. 55 X 106 psi
c. 12 X 106 psi
d. 10 X 106 psi

i think it would be 5

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