Answer: Very little effect at all. If the cannon is firing rapidly, the vibration of the gun can be transmitted to the airplanes structure. A cannon bullet is very small in size and mass. On the other hand, the Jet has a very large mass. The Laws of Physics would show that the small mass would not be able to change the momemtum(or velocity) of the larger Jet.
Answer: Well depending on what sex you are and/or your sexual orientation, you could have sex, or play with each other. Also sports, and taking long hot showers after you are done playing so you can play with each other there too!