Question for mandrin

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lia41985

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Take the moon in orbit. We all agree that "Gravity" is what's keeping the moon from flying away right? Well if GRAVITY is pulling on the moon, where is centripetal force? You can't have gravity AND centripetal force or else the pull is twice what "centrifugal" force is and we're all doomed. That's why "centrifugal" is just an interchangable word acting as a placeholder for the actual force being exerted. It DOESNT actualy exist as a force.
Do you know anything? GRAVITY IS THE CENTRIPETAL FORCE! YOU ARE GOING FROM SOUNDING DESPERATE TO SOUNDING DUMB.
 

lia41985

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Remember that an object in motion tends to stay in motion LINEAR. It only knows back, forward or not at all. In order for it to move circularly it must constantly be pulled off of it's straight course.
Again, you're sounding dumb. Yeah--back, forward if you're using ONE DIMENSIONAL KINEMATICS. Linear motion is TWO DIMENSIONAL KINEMATICS--back, forward, up, and down. WOW! This is so basic it's ridiculous. And you still have it TOTALLY WRONG!You don't understand circular motion. The object is accelerating away from the center due to centrifugal force and is being held in a circle by centripetal force. So no, you're statement about what needs to be "in order..." is completely wrong. Newton's 3rd law applies. You've only used 1 force. DUH! YOU NEED 2. So far, you've shown yourself to be an F- physics student. Keep trying.
 
Again, you're sounding dumb. Yeah--back, forward if you're using ONE DIMENSIONAL KINEMATICS. Linear motion is TWO DIMENSIONAL KINEMATICS--back, forward, up, and down. WOW! This is so basic it's ridiculous. And you still have it TOTALLY WRONG!You don't understand circular motion. The object is accelerating away from the center due to centrifugal force and is being held in a circle by centripetal force. So no, you're statement about what needs to be "in order..." is completely wrong. Newton's 3rd law applies. You've only used 1 force. DUH! YOU NEED 2. So far, you've shown yourself to be an F- physics student. Keep trying.

Ok, anyone who can read this already knows that you've gone far beyond any reasonable discussion... but just to prove the point in it's finality.

lin·e·ar - Involving measurement in one dimension only; pertaining to length: linear measure.

(http://dictionary.reference.com/browse/linear)

Now can we all agree that lia is just in here to disrupt any actual discourse?
 

lia41985

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Wow, I know, you don't know basic physics. Your strategy: google, gotcha, gaggle, then repeat. Listen, if you're trying to get back at mandrin for him being condescending to you, why go about it this way. All you're doing is you're arguing against an expert with CRAP. Why don't you just man up, tell him to apologize, and move on. And if you do, I'll get off your back. In the mean time, seeing as how you've stuck with your strategy, I'm going to stick with call you out on it.
 

lia41985

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Ringer, another gotcha--first trying to get mandrin, and now me. Linear can be up or down or back and forward. That's my point. The kinematics are two dimensional. So sorry to burst your bubble.
 
Ringer, another gotcha--first trying to get mandrin, and now me. Linear can be up or down or back and forward. That's my point. The kinematics are two dimensional. So sorry to burst your bubble.

Oh good god man. Have you never heard of linear time? Linear is the measurement in ONE direction reguardless of which dimension. Where did you graduate from again?
 

lia41985

New member
Wait, can you read? You're missing my larger point which is: do you not see the sheer ridiculousness in trying to apply rules pertaining to linear motion to circular motion? Circular motion is two-dimensional. Linear motion, as you correctly point out, is one dimensional. And when I made my two-dimensional comment about linear motion, what I meant was that lines can be one of actually three, but usally thought of as being in, one of two dimensions--vertical (up/down) and horizontal (left/right). So again, your gotcha strategy has FAILED.
Remember that an object in motion tends to stay in motion LINEAR. It only knows back, forward or not at all. In order for it to move circularly it must constantly be pulled off of it's straight course.
 
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I read this perfectly well..

Linear motion is TWO DIMENSIONAL KINEMATICS--back, forward, up, and down.

Which is about as wrong of a statement as you can possibly make. Linear motion is 1 dimentional, 2 directions. You are trying to say it's 2 dimensions and 4 directions. I don't think you have any idea how silly you are sounding with your vitriolic disgust for me.
 

lia41985

New member
Take the moon in orbit. We all agree that "Gravity" is what's keeping the moon from flying away right? Well if GRAVITY is pulling on the moon, where is centripetal force? You can't have gravity AND centripetal force or else the pull is twice what "centrifugal" force is and we're all doomed. That's why "centrifugal" is just an interchangable word acting as a placeholder for the actual force being exerted. It DOESNT actualy exist as a force.
Explain, Mr. Gotcha err...Ringer
 
So if I throw a baseball at my television, the force exerted on the television by the baseball is inertial force, yes? Could inertial force also be classified as momentum (mass*velocity)? Or is this a way of measuring the amount of "inertial force?"

I ask because a clarity in the terms surrounding the debate over centrifugal force would be helpful.
holeout,

Baseball/television interaction - corrrect. However, momentum and force are two different things.

Inertial forces manifest themselves as either a force, [(mass x length)/time^2] or torque, [mass x length^2)time^2]. In a golf swing, due to the rotational nature of the action, the inertial forces, acting on the various mass particles, are converted into inertial torques.
 

JeffM

New member
Steve - I am a little surprised by your tendency to logically bounce around when arguing. It is obvious that centripetal forces and gravity are two different forces. When we swing a ball-attached-to-a-string around in a circle, we know that we are not talking about gravity.

Regarding the automobile going around a bend at too fast a speed -there is no centripetal force at play. The automobile was initially going in a straight line, and then tried to maintain the SAME speed around a bend. In other words, it was trying to move along a circular path, rather than a straight line path. However, the subsequent sense of imbalance would give a prudent driver a strong sense of a force at play (centrifugal force) that causes this "sense of imbalance" and the driver automatically senses a need for an additional force (centripetal force) to keep the automobile in a state of balance.

Note that I have used the word "sense". I think that one can sense forces at play when driving a car, and also when hitting a golf ball. I am constantly aware that I need a "force" to keep the golf club swinging around my body along an inclined rounded-arc (circle) when executing a full golf swing, and I am fully aware of the potential consequence of NOT having that "force" in play (eg. if I let go of the golf club in the early followthrough and see the golf club fly away in the direction of the target).

Jeff.
 
Mandrin,

I remember you using the term "inertial force." But before that you had stated that inertia is not a force.

So now I'm curious: what is inertial force?

Inertia is determined by how much mass an object has, rotational inertia is determined not only by the amount of mass, but where the mass is located in reference to the axis of rotation. Rotational inertia increases with the square of the distance between the mass from the axis of rotation.
 
If I understand these things correctly:

Centrifugal force exists from the point of view of the observer, like a guy standing next to me (or myself, for that matter) while I swing a yo-yo around in a circle. But from the reference point of a small firefly trapped inside of the yo-yo, who all the while is being thrown against the outside wall of the yo-yo (and becoming very dizzy), this is a "ficticious force."

This is what I gathered from Wikipedia ;), so take it with a grain of salt. I'm just trying to sort this out for myself.
 
If I understand these things correctly:

Centrifugal force exists from the point of view of the observer, like a guy standing next to me (or myself, for that matter) while I swing a yo-yo around in a circle. But from the reference point of a small firefly trapped inside of the yo-yo, who all the while is being thrown against the outside wall of the yo-yo (and becoming very dizzy), this is a "ficticious force."

This is what I gathered from Wikipedia ;), so take it with a grain of salt. I'm just trying to sort this out for myself.
holeout,

You got it. In the reference frame, formed by the inside space of the yo-yo, the firefly has to imagine a fictitious force which is apparently forcing him again the wall.
 

dbl

New
Holeout, for an inertial force being felt, think of two people in a car going around a curve, and the inner person pressing on the outer person who is squished against the door.

--
The wikipedia article on centrifugal force had an external link to a page describing the two frames of reference (rotating and not) and the action happening with a cassette tape left on the dashboard of car going through a curve. Pretty neat graphic:

casette.gif
 
Steve - I am a little surprised by your tendency to logically bounce around when arguing. It is obvious that centripetal forces and gravity are two different forces. When we swing a ball-attached-to-a-string around in a circle, we know that we are not talking about gravity.
In that example I am not talking about a ball and string I'm talking about the moon and earth. The "centripetal" force is gravity. "Centrifugal" is the momentum of the moon. It's the same interaction as the ball and string but different forces at work.

Regarding the automobile going around a bend at too fast a speed -there is no centripetal force at play. The automobile was initially going in a straight line, and then tried to maintain the SAME speed around a bend. In other words, it was trying to move along a circular path, rather than a straight line path. However, the subsequent sense of imbalance would give a prudent driver a strong sense of a force at play (centrifugal force) that causes this "sense of imbalance" and the driver automatically senses a need for an additional force (centripetal force) to keep the automobile in a state of balance.
Ok, I'm just going to point out here why this is way over complicated. You JUST said "there is no centripetal force at play", but then you went on to tell me "automatically senses a need for an additional force (centripetal force) to keep the automobile in a state of balance".

My friend, I am not the one jumping around here.

There is no OUTWARD force on the driver. There is only MOMENTUM trying to make them go straight. When the the car makes it's turn it is moving off course of that linear movement. The momentum is still going to try and make them go STRAIGHT. If there was Centrifugal force then that would imply there is a force BESIDES momentum at play... which there is not. It's a made up term to put in for that "pull" you feel when being pulled off the linear path. But it is NOT a force.

Note that I have used the word "sense". I think that one can sense forces at play when driving a car, and also when hitting a golf ball. I am constantly aware that I need a "force" to keep the golf club swinging around my body along an inclined rounded-arc (circle) when executing a full golf swing, and I am fully aware of the potential consequence of NOT having that "force" in play (eg. if I let go of the golf club in the early followthrough and see the golf club fly away in the direction of the target).

Jeff.
All I'm saying is that the "force" you feel is centripetal...not centrifugal... and even centripetal doesn't really exist as a "force". It's just a placeholder for whatever the actual force is involved. Small, weak, gravity, electromagnetic... whatever.
 
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If I understand these things correctly:

Centrifugal force exists from the point of view of the observer, like a guy standing next to me (or myself, for that matter) while I swing a yo-yo around in a circle. But from the reference point of a small firefly trapped inside of the yo-yo, who all the while is being thrown against the outside wall of the yo-yo (and becoming very dizzy), this is a "ficticious force."

This is what I gathered from Wikipedia ;), so take it with a grain of salt. I'm just trying to sort this out for myself.

As Mandrin said, yes. You have it. The fly won't know why it's being thrown against the wall because he has no third object to base his information on. He only knows that he's stuck to a wall.
 
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