Two heavy railway vehicles are free to roll on straight, level tracks. they can be considered to be rigid bodies that are elastically connected to each other by a horizontal spring. one of them is also elastically connected to an immovable ground support by a similar horizontal spring.
how many natural frequencies and mode shapes does this system have?

Select light for the type of wave, adjust the wavelength so that the light is red, and increase the amplitude of the light to the max. then, select the start button at the source location to begin producing the waves. light is a form of electromagnetic wave, containing oscillating electric and magnetic fields. the wave amplitude detector mentioned above shows how the electric field oscillates in time at the location of the probe. the amplitude of the wave at the location of the probe is equal to the maximum electric field measured. how does the amplitude of the wave depend on the distance from the source?