| /
|/  /--------
   /  excess
   \  lead
|\  \--------
| \

> >  <- no force   cutter  force applied ->

> Your physics doesn't add up.  If "all the energy" goes into
> the excess lead, it will presumably be converted to kinetic
> energy of that lead causing it to fly off

If the leftmost edge is perpendicular to the lead and remains
so during the cut surely it can't impart any horizontal force in
the leftward direction ?

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