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.
In its basic form, a rocket is a device which propels itself by emitting a jet of matter. The momentum carried away by the jet results in a force, acting so as to accelerate the rocket in the direction opposite to that of the jet. This is familiar to us all â from games with deflating toy balloons, if nothing else.