Force is a comparative measurement just like damage is. You don't actually see the health of your opponents or their damage mitigation, however because ability "A" does more damage than ability "B", than ability "A" must logically take more squares off the enemies health meter.
The same holds true for force. If ability "A" has more newtons of force than ability "B", then it will push the enemy further, or higher or whatever you are trying to achieve. If your trying to translate damage into force, you are really just translating two non-numeric relative measurements.
Also note that impact force can affect shields as well, for example Shockwave. This is again an abstract measurement, if an ability has more force than another ability, the ability with more force will cause more damage to the target's shield.
Edit, here is a technical diagram I drew in paint:
Here I used Throw to push away a Husk. The Husk was in melee range and I threw it back with 600N of force, and it ended 6 "strides" away from me. A stride being one full step from Shepard. Note that the effect was not the same (or even close) on much more armored opponents. This effect was reproducible on two more Husks. I currently do not have any other ability that exerts "force" to test.
edit 3, conclusion
Here I used Throw rank 3 to push away another Husk, the same conditions applied. This was tested twice.
This means an extra 180N of force produced an extra 2 "strides" of pushing distance. However we can account for rounding problems in calculating strides to conclude that,
On a Husk (~200lb?), 100N of force equals 1 stride of "pushing power" at a plane of force perpendicular to the ground.