All 3 Uses of

impetus
in
Jane Eyre

I saw that in another moment, and with one impetus of frenzy more, I should be able to do nothing with him.†
p. 349.2 *

You will see what impetus would be given to your efforts and mine by our physical and mental union in marriage: the only union that gives a character of permanent conformity to the destinies and designs of human beings; and, passing over all minor caprices —all trivial difficulties and delicacies of feeling — all scruple about the degree, kind, strength or tenderness of mere personal inclination — you will hasten to enter into that union at once.†
p. 469.6

I felt veneration for St. John — veneration so strong that its impetus thrust me at once to the point I had so long shunned.†
p. 482.1

Definition:

a force that causes something or helps it move