The word is oscillation.
Reciprocating.
A back-and-forth or reciprocating movement is known as an oscillation. An example would be the motion of a pendulum. Closely related words include flux, undulation, pulsation, cycle, vibration, alternation, and see-saw(ing).
loner star
back in forth movement is the anwser
if you mean where they rub sideways against eachother then that is called the transform movement.
The back and forth movement is most commonly attributed to oscillations.
they vibrate back and forth.
A
No, it is not a preposition.Used for a verb, it is a compound adverb: going back, and forth.Used to describe a movement, it is a compound adjective: a back-and-forth motion
longitudinal vibration
A vibration.
Another way to say "back and forth" is "to and fro."