In Compton scattering, this entity's vector is parallel to the velocity vector between that of the original photon and the newly emitted photon; in rocket science, its specific variety is used to compare the efficiencies of engines in relation to propellant required, and, in classical mechanics, it is derived from Newton's 2nd Law as the integral of the time-derivative of momentum with regards to time.  
In Compton scattering, this entity's vector is parallel to the velocity vector between that of the original photon and the newly emitted photon; in rocket science, its specific variety is used to compare the efficiencies of engines in relation to propellant required, and, in classical mechanics, it is derived from Newton's 2nd Law as the integral of the time-derivative of momentum with regards to time.  FTP give the name of the product of average force times time, or, simply, change in momentum.          |
In Compton scattering, this entity's vector is parallel to the velocity vector between that of the original photon and the newly emitted photon; in rocket science, its specific variety is used to compare the efficiencies of engines in relation to propellant required, and, in classical mechanics, it is derived from Newton's 2nd Law as the integral of the time-derivative of momentum with regards to time.  
{Impulse}