Originally Posted by shonny7
There is no conceptual spring as constant force. Each spring is elastic in its nature, as you apply some force on it, it elongates. Now you could have linear or non-linear behavior of spring force-elongation curve. For ex. consider a spring which elongates by 1 mm after an application of 1 N, this is linear behavior, contrary to this; consider spring which elongates first 1mm, then .5mm, then .25,, etc, the behavior is non-linear.
In conclusion, at any given force, spring would elongate, and based on application of the force spring length will change. So, point is you couldnt really have constant force spring. There are heavy duty springs which applies constant force/dissipate similar amount of energy, but they need a static or dynamic equilibrium, which is very difficult to obtain. Anyway, hope this helps.