QUOTE(Mynck @ Aug 21 2006, 09:31 PM)
One thing though. Consider two people who can each push with 100 newtons of force. Now consider a 50kg box that they each push. Friction causes a drag of 50kg on the box. One person alone could accelerate it at 1m/s
2. Both people working together could push the box at 3m/s
2There's quite a bit missing, from your calculations, so my boring explanation shall follow in the spoiler...
» Click to show Spoiler - click again to hide... «
Let us consult a diagram...

If the box's weight is 50kg, times 9.8, gravity (G) is applying a force of 490 Newtons. The natural force (N) is obviously also 490 Newtons.
Now, to find the frictional force, we first need a coefficient of friction (static in this case) (mu(whose ASCII number I do not know...) sub s). Let's assume it's .5 (total guess). Therefore the highest the applied force could be before causing the box to accellerate would be just below 245 Newtons.
Say we have two people who each can each exert a force of 245 Newtons. Either one or both apply their force, and the box starts to move. Immediatly, since the box is now in motion, we need a new coefficient of friction (kinetic now). Let's say it's .4. (another wild guess.)
Say only one person is pushing now. They are applying 245 Newtons of force, while the frictional force has dropped to 196. There is a net force of 49 Newtons in the direction of the applied force, so the box shall accelerate at... .98 m/s
2. If two people were each to apply 245 Newtons of force, for a total of 490, there would be a net force of 294 Newtons, for an accelleration of 5.88m/s
2The reason that 2 will accelerate the box at a higher rate is only because the first 196 Newtons of force is wasted overcoming the frictional force. The added force of the second person doesnt double the acceleration, but multiplies it by a factor of the ratio of the new force to the old net force.
In a frictionless environment, this would not be the case, as friction would not have to be overcome.
Edit: and all of this is irrelevant, because it doesnt prove that 1N + 1N = 3N, only that a box can be accelerated at a higher rate by increasing the force applied to it... which we already knew.