I think you get the point but the movment of ions IS a force, meaning you can calculate it or (better example in biochemistry ) translates it in another force. this way, the transfert of H+ ions throught the mitochondria membrane is converted in heat, and mostly in the regeneration of ADP to ATP. another example should be the transfert of seve in tree from roots to leaf : the osmotic pressure is able to elevate a volume of water versus the gravity force of the weight of the water. keep in mind if zero force is involved, any system should be considered at equilibrium. equilibrium in life means death.