Re: UA and Inclined Planes
« Reply #20 on: October 20, 2019, 08:32:45 PM »
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Now imagine you accelerate the inclines plane upwards. The plane now exerts a force upwards on the ball. So the ball is pushing down on the plane. But because the plane is inclined a part of that force acts down the slope, so it moves (assuming that force is greater than the friction force). No?

No.  I explained this is in an earlier post.  The force the object exerts on the plane is cancelled out by the perpendicular force of the accelerating force.  The only force left to accelerate the object is the force parallel to the incline, and it will accelerate the object in the direction of the force. 

I have already showed the calculations using the standard formula for determining the force on an object on an incline in a gravity environment.  If you use the same formula and reverse the directions of the accelerating force and normal force, so it reflects a UA environment...you end up with the object being accelerated up the incline...not down.

Let me know if you want me to repost the explanations.

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Re: UA and Inclined Planes
« Reply #21 on: October 20, 2019, 08:53:53 PM »
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Now imagine you accelerate the inclines plane upwards. The plane now exerts a force upwards on the ball. So the ball is pushing down on the plane. But because the plane is inclined a part of that force acts down the slope, so it moves (assuming that force is greater than the friction force). No?

No.  I explained this is in an earlier post.  The force the object exerts on the plane is cancelled out by the perpendicular force of the accelerating force.  The only force left to accelerate the object is the force parallel to the incline, and it will accelerate the object in the direction of the force. 

I have already showed the calculations using the standard formula for determining the force on an object on an incline in a gravity environment.  If you use the same formula and reverse the directions of the accelerating force and normal force, so it reflects a UA environment...you end up with the object being accelerated up the incline...not down.

Let me know if you want me to repost the explanations.

Your calculation does not convert the excess force in to a tangential force to make the object rotate, it is just a generalization.  In either case if the friction is too high, the object will not move relative to the coordinates of the slope, but if the friction is low enough the object will begin to rotate.  If the slope is accelerating upwards, the rotating objects coordinates relative to the slope will translate from it's apex or top down to it's base.  If it is gravity... it will do the same.
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Re: UA and Inclined Planes
« Reply #22 on: October 20, 2019, 10:10:30 PM »
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Your calculation does not convert the excess force in to a tangential force to make the object rotate, it is just a generalization.  In either case if the friction is too high, the object will not move relative to the coordinates of the slope, but if the friction is low enough the object will begin to rotate.  If the slope is accelerating upwards, the rotating objects coordinates relative to the slope will translate from it's apex or top down to it's base.  If it is gravity... it will do the same.

I don't know where you are getting "rolling" from, as I never specified the object as round...but whatever.  Perhaps you can provide the formula and calculations that would demonstrate that that a ball on an incline that is being accelerated up , would actually roll down the incline.

That is the original question I asked.

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Re: UA and Inclined Planes
« Reply #23 on: October 20, 2019, 10:31:03 PM »
You know how to do the math, you don't know how to interpret Newtonian Mechanics.  It's that simple.  You did the math up above, but reached an improper conclusion because you don't understand how to analyze the system. If you interpret the plane as at rest, then it looks like the object slides down the hill, if you interpret the object as at rest, then it looks like the plane rises upwards.

Sorry about misreading the original problem though.  If friction was ignored, then we are just looking at the inclined plane slipping past the object at rest.
You don't get races of anything ... accept people.

Re: UA and Inclined Planes
« Reply #24 on: October 21, 2019, 12:19:24 AM »
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If you interpret the plane as at rest, then it looks like the object slides down the hill, if you interpret the object as at rest, then it looks like the plane rises upwards.

Under what circumstance would one ever interpret the object as being at rest?  In neither scenario is the object just sitting motionless on the plane (assuming the angle is sufficient).

In both scenarios, the plane would be at rest and the object is moving.  The question is just whether it is up or down the incline.

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Re: UA and Inclined Planes
« Reply #25 on: October 21, 2019, 12:39:51 AM »
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If you interpret the plane as at rest, then it looks like the object slides down the hill, if you interpret the object as at rest, then it looks like the plane rises upwards.

Under what circumstance would one ever interpret the object as being at rest?  In neither scenario is the object just sitting motionless on the plane (assuming the angle is sufficient).

In both scenarios, the plane would be at rest and the object is moving.  The question is just whether it is up or down the incline.

Im out. You have no understanding of simple Newtonian relativity and are trying to argue against the equivalence principle. Good luck to you.
You don't get races of anything ... accept people.

Re: UA and Inclined Planes
« Reply #26 on: October 21, 2019, 02:07:33 AM »
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Im out. You have no understanding of simple Newtonian relativity and are trying to argue against the equivalence principle. Good luck to you.

LOL, I understand enough of Newtonian relativity to know that if you are ever able to interpret something as being accelerated up...the equivalence principle isn't it play.

Its sort of the whole point of EP that you can't tell if something is being accelerated up or down.  You can't have it both ways.

I also understand EP enough to know that it doesn't mean "that every gravitational field (e.g.  , the one associated with the Earth) can be produced by acceleration  of the coordinate  system.  It only asserts that the qualities of physical  space, as they present themselves from an accelerated coordinate system, represent a special case of the gravitational field."

But yet people want to just apply it willynilly to any situation that suits them without explaining why or how it would apply in any given situation.  It this situation, it specifically does not apply to objects on an incline.  EP only applies to free falling objects. Objects on a inclined plane are not free falling.
« Last Edit: October 21, 2019, 02:15:06 AM by pricelesspearl »

Re: UA and Inclined Planes
« Reply #27 on: October 21, 2019, 08:38:42 AM »
Its sort of the whole point of EP that you can't tell if something is being accelerated up or down.  You can't have it both ways.

Hmm. I think the point of it is if you're in a lift and feel a force on your feet - as in, you have weight, weight is a force - you can't tell whether you are stationary and there is a force acting downwards or whether you are in a weightless environment and the lift is accelerating upwards

http://www.einstein-online.info/spotlights/equivalence_principle.html

If there is a force acting downwards because of gravity then this is how the forces work (simplifying, ignoring friction)



That diagram is exactly the same if the force is caused by an upwards acceleration rather than a gravitational field.

You are not getting any support here from FE or RE people - when everyone is telling you that you're wrong then it might be worth considering whether you are.
« Last Edit: October 21, 2019, 09:28:08 AM by AllAroundTheWorld »
If you are making your claim without evidence then we can discard it without evidence.

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Re: UA and Inclined Planes
« Reply #28 on: October 21, 2019, 09:08:16 AM »
Objects on a inclined plane are not free falling.

How so?
Not much is known about the celestial bodies and their distances.

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Re: UA and Inclined Planes
« Reply #29 on: October 24, 2019, 03:29:15 AM »
This person is an embarrassment to the scientific community.

Sorry dude/duchess but seriously why can't you grasp the simplest concepts in physics?

Seriously, if you are not schooled in the physical sciences, why come here and expound concepts just a flawed as the FE?

Sorry to be so blunt, but you have no more understanding of inclined planes under acceleration than you do of bubble levels under the same conditions.

I appreciate your position, but you seriously need a tutor or you need to do a lot more study before publicly humiliating yourself.
Here a quack, there a quack, everywhere a quack quack.

Re: UA and Inclined Planes
« Reply #30 on: October 24, 2019, 12:30:40 PM »

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That diagram is exactly the same if the force is caused by an upwards acceleration rather than a gravitational field.

Not exactly, the directions of the accelerating and normal forces would be reversed, but otherwise it would be the same. The calculations for determining the amount of force is exactly the same as well.  I pointed that out earlier.  The difference is that with the gravity calculations, the result is X amount of force pulling the object down an with UA, it is X amount of force pushing something up.

From an earlier post

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Net Gravitational force 10kg @ 20 ⁰
 Fnorm = 10.000 * 9.810 * cos(20) = 92.184N
 F⊥= 10.000 * 9.810 * cos(20) = 92.184N
F// = 0.000 * 9.810 * sin(20) = 33.552N
The normal and perpendicular forces cancel each other out, so the net gravitational force is 33.552N.  The net UA force would be the same, but in the opposite direction.  How does that account for being accelerated downhill?

Net Gravitational force 10kg @ 30 ⁰
Fnorm = 10.000 * 9.810 * cos(30) = 84.957N
F⊥= 10.000 * 9.810 * cos(30) = 84.957N
F// =   10.000 * 9.810 * sin(30) = 49.050N
The normal and perpendicular forces cancel each other out, so the net gravitational force is 49.050N...same question as above.

Interesting observation…the net gravitational force increases as the angle increases.  It’s almost as if the magnitude of the net gravitational forces on something change in response to how level it is. 

The accelerating force is proportionally divided between the perpendicular and parallel, the perpendicular and normal forces cancel each other out, leaving only the parallel force to accelerate the object.  If that accelerating force is UA, then the object will be accelerated up, if you use the same formula.

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Acceleration is produced by a net force on an object and is directly proportional to the magnitude of the force, in the same direction as the force, and is inversely proportional to the mass of the object.
Acceleration = Force/mass (a = F/m)


http://www.csun.edu/~psk17793/S9CP/S9%20Acceleration.htm


Re: UA and Inclined Planes
« Reply #31 on: October 24, 2019, 01:27:20 PM »
Acceleration is produced by a net force on an object and is directly proportional to the magnitude of the force, in the same direction as the force, and is inversely proportional to the mass of the object.
Acceleration = Force/mass (a = F/m)
Indeed. But, and this is the point you are repeatedly failing to understand, the object pushes DOWN on the inclined plane BECAUSE (under UA) the plane pushes UPWARDS on the object.
Newton's third law.

https://www.physicsclassroom.com/class/newtlaws/Lesson-4/Newton-s-Third-Law

The only difference under a gravitational field is that gravity causes the ball to push down on the plane, that causes the plane to push back up on the ball.
The cause of the force is different but the action and reaction forces are equivalent. That is the entire premise of the equivalence principle.

In either case the object pushes down on the plane so it goes down the slope, assuming the force down the incline is greater than gravity acting up it.

You ARE wrong about this, you just don't understand all this as well as you think you do. It's worth noting that literally everyone - FE and RE, including Einstein - is telling you than you're wrong.
So...you know, it's probably you, not everyone else.
If you are making your claim without evidence then we can discard it without evidence.

Re: UA and Inclined Planes
« Reply #32 on: October 24, 2019, 02:37:35 PM »
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How so?

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Free fall occurs whenever an object is acted upon by gravity alone.
https://physics.info/falling/

An object on an incline would be affected by both friction and normal force.  An object in free fall cannot be supported because free fall implies weightlessness.  When an object is supported, normal force creates the sensation of weight.  The Equivalence Principle only applies to unsupported, free falling objects.

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Free Fall-  the term given to the motion of an unsupported object under the infulence of gravity
https://www.quia.com/jg/2434543list.html

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The equivalence principle tells us that the "force" of gravity is the same as the pseudo-force effecting unsupported bodies in an accelerated frame of reference, and it is regarded as central to GR
https://www.researchgate.net/post/What_is_the_relationship_between_the_equivalence_principle_and_general_covariance_in_GR
 
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The last thing we have to consider in our experiment is that a ball rolling down an inclined plane is not in free-fall. The inclined plane exerts some force on the ball
http://www.bu.edu/astronomy/files/2014/02/Gravity-New2014.pdf

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“At the same location all unsupported objects fall towards the center of the earth at the same constant acceleration”

https://web2.ph.utexas.edu/~coker2/index.files/freefall.htm

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Einstein's general theory of relativity, announced in 1915, uses the principle of equivalence to explain the force of gravity. There are two logically equivalent statements of this principle

First, consider an enclosed room on the Earth. In it, one feels a downward gravitational force. This force is what we call weight; it causes unsupported objects to accelerate downward at a rate of 32 ft/s2 (9.8 m/s2). Now imagine an identical room located in space, far from any masses. There will be no gravitational forces in the room, but if the room is accelerated "upward" (in the direction of its ceiling) at 9.8 m/s2—say, by a rocket attacked to its base—then unsupported objects in the room will accelerate toward its floor[/bold]at rate of 9.8 m/s2, and a person standing in the room will feel normal Earth weight.

https://science.jrank.org/pages/5790/Relativity-General.html

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“…for example, there is allegedly no way to distinguish the assertion that all unsupported objects of a certain class fall to the ground from the assertion that [bold]unsupported objects [/bold]in that class near the earth are attracted by the earth according to Galileo’s law of free fall.”

https://books.google.com/books?id=lXda41Q0FgIC&pg=PA266&lpg=PA266&dq=%22for+example,+there+is+allegedly+no+way+to+distinguish+the+assertion%22&source=bl&ots=VN9nLq2Xl9&sig=ACfU3U1qA5EMZly8XjeP97dtf44MOPLR_w&hl=en&sa=X&ved=2ahUKEwicsIWEj7XlAhUGZd8KHdu5CTcQ6AEwAHoECAAQAg#v=onepage&q=%22for%20example%2C%20there%20is%20allegedly%20no%20way%20to%20distinguish%20the%20assertion%22&f=false


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5.15 Freely Falling Bodies

We know from everyday experience that unsupported objects located at some height tend to fall towards the ground.

https://books.google.com/books?id=wjs_DAAAQBAJ&pg=SA5-PA31&lpg=SA5-PA31&dq=%22freely+falling%22++%22unsupported+objects%22&source=bl&ots=0rT2NDwxSc&sig=ACfU3U2wS03WU6DKmMRYIGCTGR_bOkf_Yw&hl=en&sa=X&ved=2ahUKEwi_3eWpjLXlAhUlmeAKHXdTBrwQ6AEwCXoECAcQAg#v=onepage&q=%22freely%20falling%22%20%20%22unsupported%20objects%22&f=false
« Last Edit: October 24, 2019, 03:20:03 PM by pricelesspearl »

Re: UA and Inclined Planes
« Reply #33 on: October 24, 2019, 03:10:30 PM »
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Indeed. But, and this is the point you are repeatedly failing to understand, the object pushes DOWN on the inclined plane BECAUSE (under UA) the plane pushes UPWARDS on the object. Newton's third law
.

No, what you are failing to understand is the UPWARDS force that would exist with gravity and downwards force that would exist with UA which is called the Normal Force, is cancelled out by the perpendicular force. Resulting in the effect of no upwards force at all.

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The normal force is the support force exerted upon an object that is in contact with another stable object. For example, if a book is resting upon a surface, then the surface is exerting an upward force upon the book in order to support the weight of the book.
https://www.physicsclassroom.com/Class/newtlaws/U2L2b.cfm#norm

In a gravity environment, the normal force will produce an upward force to balance the downward effect of gravity.  In UA, it would be the opposite.  The normal force would produce a downward force to balance the upward effect of UA.
However...
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The vertical forces (perpendicular to the incline) (which would be gravity or UA) cancel out, because the normal force equals the perpendicular component of the weight force; thus, we are only looking at forces parallel to the incline.
https://socratic.org/questions/an-object-with-a-mass-of-5-kg-is-on-a-plane-with-an-incline-of-pi-8-if-the-objec-3

IOW, the net force between the object and the plane is zero. The plane is pushing on the object with the same force as the object is pushing on the plane so the net result is zero force.  There is no force between the object and the plane.

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Newton's first law states that an object that remains in uniform motion will remain in uniform motion unless it is acted upon by an external force. This also includes that an object at rest will remain at rest unless it is acted upon by an external force. When more than one force acts upon an object, the vector sum of these forces is the resultant force.
https://en.wikibooks.org/wiki/Statics/Newton%27s_Laws_and_Equilibrium

Since the normal force and the perpendicular force cancel each other out, the resultant force is the parallel force only.

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The perpendicular component of the force of gravity is directed opposite the normal force and as such balances the normal force. The parallel component of the force of gravity is not balanced by any other force. This object will subsequently accelerate down the inclined plane due to the presence of an unbalanced force.[bold] It is the parallel component of the force of gravity that causes this acceleration.[/bold] The parallel component of the force of gravity is the net force
.

If it is the parallel component of gravity which accelerates an object down,  the parallel component of UA would accelerate it up. There is no other forces (assuming no friction or applied force) working on the object that could cause it to accelerate down.

https://www.physicsclassroom.com/class/vectors/Lesson-3/Inclined-Planes


« Last Edit: October 24, 2019, 08:14:33 PM by pricelesspearl »