Answer: The net force acting on an object is the sum of all the force acting on it, and the net force of an object is zero. I f the forces acting on it tend to cancel each other. For example you are sit in a chair, the earth's gravity is pulling you down, but the chair is pushing you up with an equal amount of force.
There is my answer from my notebook .I hope its good :)
<h3>that`s a the train car, that you asked the meaning, of that if the train car rolls it`s doing it`s speed, and it`s not ganna fall off the the trail of the train, car.</h3>
