A boat is travelling due west at a speed of 47 miles per hour. If the boat started off 170 miles directly north of the city of Smithville, how fast is the distance between the boat and Smithville changing when the boat has travelled 78 miles

An electromagnetic wave with frequency 65.0 hz travels in aninsulating magnetic material that has dielectric constant 3.64 andrelative permeability 5.18 at this frequency. the electric fieldhas amplitude 7.20 \times 10^{ - 3} {\rm v}/{\rm m}. a. what is the speed of propagation of the wave? b.what is the wavelength of the wave? c.what is the amplitude of the magnetic field? d.what is the intensity of the wave?