I need help on Newton's first law.?

Question

I know what it is, but I don't really get it. The whole "Net Force" and junk is a bit confusing to me. Someone please help?

Answer 1

Net Force really is just talking about the sum of the forces that come in contact with an object that can change its velocity. Everything on Earth has some sort of Force because of Gravity - gravity pulls towards the center of the earth causing a downward Force. Air is a force on things flying - take your hand and move it through the air as you feal resistance you recognize a negative force, but take a feather and blow on it - now you have a possitive force causing the feather to move forward and also a negative force of gravity pulling it towards the ground.

What all this goes to say is that if an item has no external forces on it, it will continue to move at the same rate it is moving. If it is sitting still it will stay still if it is moving it will continue moving at a steady speed untill it comes in contact with a force of any kind.

Answer 2

Newton's First Law can be expressed like this:

Force does not cause motion. Force causes CHANGE in motion.

In other words, if there's no net force on an object, it moves at a constant velocity in a straight line (what Newton rather poetically called "uniform motion." Conversely, if an object is moving in a manner OTHER than in a straight line with constant velocity, there MUST be a net force on that object.