From The Collaborative International Dictionary of English v.0.48 [gcide]:
forcefulness \forcefulness\ n.
physical energy or intensity.
Syn: force, strength.
[WordNet 1.5]
From WordNet (r) 3.0 (2006) [wn]:
forcefulness
n 1: physical energy or intensity; "he hit with all the force he
could muster"; "it was destroyed by the strength of the
gale"; "a government has not the vitality and forcefulness
of a living man" [syn: force, forcefulness, strength]