Kevin is standing outside a railway station. he can know whether a train is approaching the station or departing from the sound it makes. which principle of sound waves is he using?

Two polarizers are oriented at 70∘∘ to one another. unpolarized light falls on them. what fraction of the light intensity is transmitted?

How much energy must a refrigerator absorb from 225 g of water so that the temperature of the water will drop from 35°c to 5°c

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?