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.
The air that is heated would push out the back, pushing the cannon in the opposite direction. This is how jets work as well as how rockets get into space. Remember, because every action has an equal and opposite reaction something will go forward if it is pushing matter behind itself.