"an act of force" is correct and usable in written English.
You can use it when you are referring to the exertion of physical strength or power to change the course of events. For example: The explosion of the bomb was an act of force that caused significant damage to the town.
Israel came into existence through an act of force majeure by the United Nations.
(Thomas Jefferson believed that any constitution should expire after nineteen years: "If it be enforced longer, it is an act of force and not of right").
As the architects put it: "It is not an act of force but a delicate adaptation to make the most of what already exists".
In fact, when it comes to Airmanship, the act of flight itself can be considered a type of controlled defiance -- an act of force against the unyielding weight of gravity.
According to The Local, he said, "At a time when religious values seem to have become insignificant and everything is commercial, it's right to feel indignation, even with an act of force".
The result was controlled - an act of forced choice – with the military carefully selecting and coercing the participants.
To the casual observer, Ms. Schenardi's dutiful slicing and rolling and kneading at that front table at Gradisca might seem like an act of forced labor: mommy martyrdom taken to a new extreme.
When the wake-up call sounded for the detainees at 5am, in an act of forced humiliation, Manning was made to stand naked at the front of his cell.
The board's directive "does not constitute an act of forcing students to follow a certain philosophy," and it is "necessary for schools to require uniformity at group-oriented ceremonies," Mr. Nakanishi wrote in the ruling.
Establishing the illegality of an act of forced displacement, for example, may require legal analysis on a case-by-case basis.
