“Preposterous twaddlecock Time travel is impossible!”
“But Professor, you time traveled yourself. Remember? When we went back to Roswell?”
“That proves nothing! And furthermore, you’d think I could remember a thing like that! Plus, who are you anyway?”
If you assume that a “bullet” is a unit of momentum (the mass and velocity of a bullet) and “square child” is actually just referring to the mass of a child who happens to be square shaped and not the mass of a child squared, then “bullets per square child” is describing valid units for a velocity