How fast must a projectile moving horizontally travel so that the curve it follows matches the curve of earth?

Awave with a frequency of 500 hz is traveling at a speed of 100 m/s.what is the wavelength?

If a star is moving toward earth, it is

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?