How to use the idiom “in force”

Question

I'm wondering how to correctly use the idiom "in force". Often "active" can be used instead, but are there any situations in which "in force" can be used and "active" cannot, or vice versa? More generally, what are the idiomatic limitations of this expression?

To illustrate, I have the following example from a text I wrote (emphasis added):

Each event has associated with it a tension weight. The tension at a particular point in the story is obtained by adding all individual tension weights in force at that particular point. [It is not specified] how to determine which tensions are in force.

In both cases, the sentence could be rewritten to use the word "active" instead, but it is incorrect to use "in force" here?

I found the following here:

in force

1. In full strength; in large numbers: Demonstrators were out in force.
2. In effect; operative: a rule that is no longer in force.

The second meaning seems to suggest that the above use of "in force" is ok.

Answer 1

Meaning 2 is often found in legal documents. A treaty or a piece of legislation will normally have a clause naming the date from which it is in force or the date from which it comes, or enters, into force. It is difficult to comment on your example without knowing the broader context, but, because of the legal connotations of ‘in force’, an alternative might be preferable.