| | net force zero = velocity > zero ?? |
 | | It's the essence of the reinterpretation of the first postulate in terms of forces (defined in the second one).The principle of inertia applies,iff the vector sum of all forces acting on the body/system is zero. |
 | | Of course that YOU are aplying a force, you are "feeling" the force you are aplying on the object, BUT, otherwise, the 1st Law says that the NET force NEED to be zero for that the actual state of rest or uniform movement (both having a=0) remains like that. |
 | | Your force on the body exists, and it will always exist in real cases because the friction, the gravity or any other sort of oposite force, but so as to know the behavior of the velocity of the body (if it´s changing or not) you need to calculate the NET force. |
| www.physicsforums.com /showthread.php?p=567850 (791 words) |