A projectile of mass m is fired horizontally from a launching device of length D, exiting with a speed vx . While the projectile is in the launching device, the impulse imparted to it is Jp , and the average force on it is Favg . Assume the force becomes zero just as the projectile reaches the end of the launching device. Express your answers in terms of vx, , Jp , Favg and fundamental constants, as appropriate.