Which statement is true of an electromagnetic wave? A. The wave needs particles in matter as a medium.
B. The wave travels through electric and magnetic fields.
C. The wave is caused by vibrating particles of matter.
D. The wave carries mechanical energy.

An important dimensionless parameter concerned with very high-speed flow is the mach number, defined as v/c, where v is the speed of the object such as an airplane or projectile, and c is the speed of sound in the fluid surrounding the object. for a projectile traveling at 1170 mph through air at 50 ˚f and standard atmospheric pressure, what is the value of the mach number?