Post by JayUtah on Feb 5, 2006 0:59:53 GMT -4
Now, where do notions of "real" and "fictional" fit in here?
The notion of "fictional" force comes from the notion that inertia doesn't count. Reaction forces don't normally count because they're universally expected. Action and reaction are inseparable.
So, perhaps the non-reality of the force I experience in the car resides in the fact that I cannot observe a cause.
Yeah, pretty much. The closed car is meant to express the idea of a reference frame. Your not being able to see out of the car mimics the omission of forces that don't appear because the reference frame moves.
But if so, then I might pester you guys about why gravity is considered a real force and not a phantom one...
Because it is not a reactive force; that's all. What makes centrifugal force a phantom force from the car's reference frame is that it can't be determined from that perspective that your tendency toward the side of the car is a reaction.
By "agent" I don't mean visible means or nefarious intent. It just has to be a direct force and not a reaction. Gravity is a direct force.
Does the centripetal force arise from the car and the earth-anchored-track resisting each other's inertia?
Yes, if your reference frame is the one that encompasses, but is independent from, either the track or the car. And it matters whether your frame is inertial or non-inertial.
Centripetal force, as I understand it, is a tendency towards a center. But there is nothing special, right, about the patch of real-estate that comprises the center of the arc of our track?
Nothing special.
Do we, then, simply call any motion around a center "an object being acted on by a centripetal force"?
In a way. Motion in anything other than a straight line would need to involve some sort of centripetal force.
The notion of "fictional" force comes from the notion that inertia doesn't count. Reaction forces don't normally count because they're universally expected. Action and reaction are inseparable.
So, perhaps the non-reality of the force I experience in the car resides in the fact that I cannot observe a cause.
Yeah, pretty much. The closed car is meant to express the idea of a reference frame. Your not being able to see out of the car mimics the omission of forces that don't appear because the reference frame moves.
But if so, then I might pester you guys about why gravity is considered a real force and not a phantom one...
Because it is not a reactive force; that's all. What makes centrifugal force a phantom force from the car's reference frame is that it can't be determined from that perspective that your tendency toward the side of the car is a reaction.
By "agent" I don't mean visible means or nefarious intent. It just has to be a direct force and not a reaction. Gravity is a direct force.
Does the centripetal force arise from the car and the earth-anchored-track resisting each other's inertia?
Yes, if your reference frame is the one that encompasses, but is independent from, either the track or the car. And it matters whether your frame is inertial or non-inertial.
Centripetal force, as I understand it, is a tendency towards a center. But there is nothing special, right, about the patch of real-estate that comprises the center of the arc of our track?
Nothing special.
Do we, then, simply call any motion around a center "an object being acted on by a centripetal force"?
In a way. Motion in anything other than a straight line would need to involve some sort of centripetal force.