Earphone definition, a sound receiver that fits in or over the ear, as of a radio or telephone. See more.
Answer Wiki. If a rocket went straight up, it would either continue in that direction and leave Earth, or it would fall back down, depending on its velocity. Most rockets intend to enter orbit, which is an elliptical trajectory, and it's much more efficient to arc into this trajectory than to go straight up and then accelerate laterally.
Understanding how these model rockets works can save you the frustration of a rocket that fails to launch or worst, that is destroyed during launch or recovery efforts. Understanding how model rockets work is also necessary for the safety of all those involved in launching and observing the flights.