How are both electromagnetic and mechanical waves used when people communicate with each other?

If a star is moving toward earth, it is

Determine the time it takes for a satellite to orbit the earth in a circular "near-earth" orbit. the definition of "near-earth" orbit is one which is at a height above the surface of the earth which is small compared to the radius of the earth, so that you may take the acceleration due to gravity as essentially the same as that on the surface. does your result depend on the mass of the satellite?

Why would an orange roll of your cafeteria tray if you stopped suddenly