I am confused as to what the difference between radial and longitudinal acceleration is . i am also unclear as to what the longitudinal axis is defined as. I am hoping someone could explain it in 'engineering terms' rather than right arm thrust and drawn from a quiver explanation. have i missed the definitions somewhere else in the book? i initial thought radial acceleration was centripetal acceleration and longitudinal acceleration was tangential acceleration but i know believe this to be incorrect. if anybody could clear this up it would be great.