Originally Posted By: Bill S.
However, I accept that trying to explain something to someone else is possibly the best way of understanding it.

Indeed. I gain a great deal from forums like this for exactly that reason.


I can see the possible answer: F=ma, so if a=0, m=0, so F=0;
..
especially where no movement is concerned. [/quote]

With no movement that equation doesn't help much. Remember F is the total force, so if it's not accelerating then there must be some other force counteracting the applied one.