Force is the essence of what causes something with mass to accelerate, and is one of the main characters in Newtons laws of motion. For most purposes in AIF, force is generally assumed to be measured in units of Newtons, and interacts with the game rules with regards to strength and gear.
When relating to strength, force is meant to be a way to simplify what sorts of feats of strength a being can accomplish. The easiest way to visualize what strength measures is probably somewhat akin to a bench press for a human, but don't take that description too far.
Feats of strength usually tested are things like:
- the maximum size of object that can be carried (usually in 1 standard Gee - 10 m/s², or 10 N/kg)
- total amount of mass that can be carried by a character without detriment (usually 1/2 maximum force)
- firing a weapon with a certain force rating for recoil - note that 1-handed use is limited to 1/2 maximum force
- comparing strength to try to hold another being in hand-to-hand combat
- inflicting additional damage in hand-to-hand combat
Meanwhile, with respect to the force rating of gear (usually weapons), this refers simultaneously and equally to the impact potential of the gear and the recoil that the user must endure. The recoil aspect is already mentioned above, and the impact potential is mentioned in the Placement Ramifications section of combat.
Lastly, in combat we typically translate every 1000 N of force to be one point of damage. For a regular range weapon to inflict this, the referee must decide that the target is sustaining the full effect of the force of the blast - usually this requires the target to be pinned against an unyielding surface. Otherwise, the target merely gets thrown some amusing distance, and needs to make an agility check to see how badly sprawled they are. In hand-to-hand combat, however, it is assumed that every hit (not including thrown objects) also imparts full force if the attacker so wishes. And they usually do.