Subject: Energy Conversion and Newton's Laws

Would half the propellent energy from a gun or rocket be wasted on the kinetic
energy of the gun's recoil or rocket's exhaust gases due to Newton's Third law
and the Conservation of momentum. Newton says for every force there is a
reactionary force so is it impossible to transfer the potiental energy into
kinetic energy of a mass without moving something else and if so isn't that
wasting energy.
Thanks for your help. 

Re: Energy Conversion and Newton's Laws