Smith66 should be banned.

[getterdone]

Just for the record , Prime, I don't belong on that list either. I've never once said anything offensive to Jim L.

My post was in support of keeping him. I think he has some good ideas.... if only he could leave all the other stuff out and focus on the mission, he'd do well here

[jim_mich]

I'm actually more dangerous than all three of these guys because I know
Physics and can use it as a weapon!

So cloud camper, you are saying you're here to fight other members, rather than help them.

[cloud camper]

My mission is to help others with their ignorance of CF/CP in rotating systems and the associated ramifications of the 1st law.

How can I serve you?

[rlortie]

cloud camper,


You can serve me by explaining why centripetal is considered or deemed a "Force"?

Centripetal is the property of physically confining a mass to a given orbit. It can be done by retention such as fixed to a spoke, maintained by a rope or rod fixed to the axis of rotation. It may also represent a fixed rim on a wheel. This physical retention of mass must be strong enough to overcome inertia making for centrifugal (which I maintain as fictitious)

The inertial force is always pulling at a tangent, The fixed centripetal mass diverts this tangent to the axis and becomes useless as a source of usable energy.

A child on a merry-go-round exhibits centripetal by hanging on to the vertical post supporting the horse, the post is not exhibiting any force nor is the outward pull of centrifugal on the child's arm assisting the rotation of the machine.

It is like pushing on an immovable wall, no work is done, we do not consider the immovable wall a force yet the same properties in an orbital path is called a "force"... Why is that???

Ralph

[cloud camper]

Ralph, the inward Centripetal force always acts to "accelerate" the otherwise linear path of the child on the merry go round.

This inward "acceleration" can be felt by the child just like a linear acceleration is felt.

Instead of accelerating linearly to the horizon the child accelerates inwards towards a fixed point.

The child accelerating inwards displays an inertial resistance to rotation that is commonly described as CF, but is called a fictitious force because nothing is causing it except the linear inertia of the child trying to resist rotation.

If it were an actual force, the child would shoot off radially from the center, but this does not occur and the child always comes off with a purely tangential trajectory.

In JM's example of the cellphone sliding across the dash, an observer looking down from a helicopter overhead would report that the cellphone
did nothing but try and continue in the same linear path it had before the steering wheel was turned.

This can be understood simply as the dashboard turning away from (out from under) the phone, not the phone sliding away from the dash.

There is no "new" energy generated here. The phone could be rigged to compress a spring but this is not "new" energy.

This is an identical situation to a person standing on a rug then having someone yank the rug out from underneath. The person standing on the
rug did not suddenly acquire "new" energy. All the work was generated by the person yanking on the rug.

This shows that the inertial resistance of the person standing on the rug is not a force and creates no new energy. This inertial resistance to change in velocity (in this case zero) shows up as CF in a rotating environment. If there were a force here the person would shoot off in the opposite direction from the yanked rug, but this does not happen.

In the sliding cellphone example we have a temporary reduction in CP holding the phone to the dashboard. For this temporary period until the phone hits the windshield on the far side, there is less work required by the tires to maintain CP for the entire vehicle (and thus less heat to maintain slip angle) and we could compress a spring.

But as the spring is compressed, the CP force then rapidly increases again due to the fact that the other end of the spring has to push on the far side of the vehicle, and will have to increase even more than a steady state no sliding phone condition since the phone must now be accelerated inwards to match the same rotation radius as the rest of the vehicle.

The same situation occurs if we simply allow the phone to hit the far side of the windshield, a large spike in CP is then required from the tires to maintain the radius of rotation, far beyond what would be required in a steady state turn situation with no sliding phone.

This CP force is generated solely by heat in the tires maintaining the exact CP value required to keep the vehicle in a steady radius of rotation.

By temporarily reducing the overall mass to be kept in rotation (sliding cell phone) we temporarily reduce the amount of CP required from the tires (and thus less heat). This is where the APPARENT work shows up as in letting the phone compress a spring.

But after the APPARENT work is performed compressing the spring, the tires must then do much more work in the form of increased heat to bring everything back into equilibrium.

Both these situations result in a pay me now or pay me later phenomenon. The temporary reduction in CP can be used to compress a
spring but we have to pay for it with more heat.

The overall result is no gain for the process.

[Trevor Lyn Whatford]

Hi CC,

I will go with Ralph on this one! It is not CP that accelerates the Earths orbits and increases CF, it is not CP that slows down the Earths orbit and reduces CF. Call it what it is, it is Gravity’s!

Yes it contravenes Known physics but I never wrote them. CP to me is Convenient Physics!

Maybe start a new thread CC as its your baby!

I am not ignorant I have researched it, but I do not agree with physics on this one.

With respect, Trevor

Edit, If CP was the true force or even equal to CF why if the chain breaks on the fair ground rotating chairs they would never fly into the middle they would fly off to seek a straight line trajectory outward.

[rlortie]

cloud camper,

I appreciate the lengthy response, however like Jim_Mich you have twisted a simple question of "why is Cp considered a force" when it is a physical entity, a barrier not forcing but retaining a rotational mass within a desired radius.

Sliding tires, telephones sliding across a dash and springs does not answer my question. If I push on the wall of the Oval Office am I met with a force, or a physical static mass to heavy for me to initiate inertia and move it?

I will make an exception for gravity, as an attractive force, it is not a physical barrier.

Once again I reiterate: Centripetal is created via a fixed mass strong enough to maintain a cancellation of inertia which tends to divert the objects velocity to a straight trajectory. If I stick the telephone on the dash with a wad of chewing gum, does the gum become a force?

I see no force in the merry-go-round vertical pole, only in the child's arm if he should attempt to pull himself inward.

Ralph

[cloud camper]

OK Ralph- I'm on my way out the door for a 3 hour bike ride so I will
get back to you on my return.

[AB Hammer]

Really sorry to disappoint you Tars.

But I'm not JL, 007 or Techstuff.

I'm actually more dangerous than all three of these guys because I know
Physics and can use it as a weapon!

I am also glad to here it. We always need a good view from inside the box, for sometimes we go a bit to far away from the box.

[cloud camper]

cloud camper,

I appreciate the lengthy response, however like Jim_Mich you have twisted a simple question of "why is Cp considered a force" when it is a physical entity, a barrier not forcing but retaining a rotational mass within a desired radius.

Sliding tires, telephones sliding across a dash and springs does not answer my question. If I push on the wall of the Oval Office am I met with a force, or a physical static mass to heavy for me to initiate inertia and move it?

I will make an exception for gravity, as an attractive force, it is not a physical barrier.

Once again I reiterate: Centripetal is created via a fixed mass strong enough to maintain a cancellation of inertia which tends to divert the objects velocity to a straight trajectory. If I stick the telephone on the dash with a wad of chewing gum, does the gum become a force?

I see no force in the merry-go-round vertical pole, only in the child's arm if he should attempt to pull himself inward.

Ralph

OK Ralph, sorry I didn't get back to you sooner but my video card crashed and I was too lazy to fix it til now.

Basically the Centripetal force is transmitted by any medium available to transmit it. So you're right, this could be the child's arm thru the wheel's handles at higher rpm's or simply friction created by the child's shoes with the wheel at lower rpm's.

A rope tied to the center hub would be another medium.

The chewing gum example you give is not a force but it can transmit a force. So it is another example of the CP force being transmitted by any means available to it.

If the child is determined to maintain rotation with the merry go round, the child must use his outstretched arm to create and transmit the CP force that will sustain the child in accelerated motion.

Simultaneous to this action, the child's inertial resistance to rotation (CF) goes into effect to oppose the CP force, causing the opposing CF/CP pair to go into existence.

This is a very interesting phenomena to me as it shows that nature does not allow an unopposed force to exist.

A defined rotation velocity for the merry go round with a defined weight for the child determines a fixed CP value that is generated and transmitted by the child's arm plus friction through the child's shoes.

It is the child's decision to rotate with the wheel that causes the CF/CP opposing pair to generate. CF cannot exist without CP and vice versa.

The instant the child reaches out with his/her arm and grabs the wheel handles, the CF/CP opposing pair come into existence. The merry go round is doing nothing different than before. The child has decided to go into accelerated (rotating) motion with the wheel and then must establish the CP force that holds him or her to the wheel.

The idea to understand here is that the CP force is instantly created essentially out of nowhere the instant the child grabs the wheel handles.
This happens as a result of a decision to go into accelerated motion with the wheel.

Of course no physical work is done once the child is in steady rotation. The child is transmitting the CP force but since there is no inward displacement in steady rotation, no work is being produced.

If the child decides to move him/herself in closer to the center, then must perform work against the child's inertial resistance to rotation (CF).

If the child decides to leave the wheel, he or she breaks the opposition between the CP force holding the child to the wheel and the inertial resistance (CF) and lets go with his/her arm. The "letting go" event is another decision by the child that instantly destroys the CF/CP opposing pair and the child leaves the wheel with whatever tangential velocity the child had acquired on the wheel.

So neither force can exist without the other even for an instant.

If you're still confused, I will continue to try and clarify.

Thanks Ralph!

[murilo]

camper,
I reach fine to your elucidation and clear explanation.

For years, in order to sleep well and stay in peace with my already suffered intellect, I use to consider/accept that CF/CP is an effect of something... NOT a cause by itself.

Best!
M

[jim_mich]

The idea to understand here is that the CP force is instantly created essentially out of nowhere the instant the child grabs the wheel handles.

Hmmm... A force is instantly created out of nowhere? Sounds like fairy dust, bunny smoke, or Hogwarts Harry Potter magic.

[rlortie]

I agree and accept the above explanation, but it is plain to see I am still not getting to the root of my question.

I agree that the properties making up "centrifugal" is created by a force known as inertia.

What I do not see and is my initial question is why do we refer to centripetal as a "force" when it is a physical impediment, impede; To retard or obstruct the progress of... In our case it obstructs a force (inertia) from traveling in a straight line making for Cf, but it in itself is not a force, or is it?

Centripetal must be moving to create force and if it moves in the direction of the force then we can call it work. Cp when only impeding is doing no work nor is Cf.

There is no fairy dust as the impediment is either there or it isn't.

Ralph

[Trevor Lyn Whatford]

Hi CC,
I have been on many fair ground ride and must confess I have never experiments a pull to the centre, it has always been a pull outward CF thus CP if it exists cannot be as strong as CF which seems to be the natural force outward of mass on spinning objects. On my motorbike I lean into the corner to reduce the effects of the CF, if I do not then there is a good chance CF will try to pull me back to a straight line and I may lose control. The child’s muscles fight against CF if not then the child will be pulled outward.

In orbiting planets you could say there is a pull to the centre, but that would be the pull of gravity’s so why call it CP. Have you seen a CP detector? it is a air pocket in a jar of fluid if the air is moved into the centre that is supposed to show CP, but to me if the air moves to the centre that means the heaver fluid mass is being pulled out by CF that is why the air moves into the centre of the ride.

There is something not right about this part of physics so I chose to question it and do my own experiments.

Regards Trevor

Edit, + outward pull on mass.

[jim_mich]

If, for some reason, CF is stronger than the restraining CP, then the object in question will be moved outward by the CF.

If, CF is weaker than the restraining CP, then the object in question will be pulled inward by the CP.

Whenever there's motion of a body either inward or outward, then work is done by either the CF or the CP. Work is defined as force acting over a distance causing a body to move.

And just as a force against a stationary body causes no work, a weight rotating at a fixed radial distance is doing no work. But when the weight is moved inward by CP or outward by CF then work is done by or to the weight.