Question about gravity.

reply to post by SplitInfinity

It is like saying that if I had a Trampoline and it was in a Vacuum chamber on Earth...and a 10 lbs ball was dropped on the trampoline...that that ball would continue to bounce forever.

If the trampoline had 100% rebound it would. No trampoline does.

If this was possible then the Human Race would have PERPETUAL MOTION MACHINES ALL OVER THE PLACE

No. Because there is always energy loss. But, if there were no friction there would be perpetual motion machines. They just couldn't do anything because to do so would take energy out of the system.

Originally posted by Phage
No. Because there is always energy loss. But, if there were no friction there would be perpetual motion machines. They just couldn't do anything because to do so would take energy out of the system.

edit on 10/21/2012 by Phage because: (no reason given)

what about perpetual machine in a vacuum chamber? like those magnet type devices? getting any type of energy needed by solar panels?

reply to post by Phage

OK...I will tell you what. Explain exactly how you believe that a Pendulum that is not effected by Friction in any way...could continue to swing and ignore the effects of Gravity? Because for that Pendulum to be able to swing...it must rise as it reaches the furthest extent of it's swing. Therefor it must counter Gravity's effect.

As far as anyone knows...NOTHING CAN ESCAPE GRAVITATIONAL EFFECT. Now how do you state that a pendulum can continue to escape Gravity's effect? Split Infinity

reply to post by SplitInfinity

Because for that Pendulum to be able to swing...it must rise as it reaches the furthest extent of it's swing. Therefor it must counter Gravity's effect.

Yes. And in doing so it acquires potential energy. Just like if you drive a car up a hill. And when it reaches the apex of its swing it has acquired a certain amount of potential energy. It then turns that potential energy into momentum as it accelerates downward. When it reaches the bottom of the swing it begins turning that momentum back into potential energy as it climbs to the other apex. Without friction the conversion of potential energy into momentum and back into potential energy is perfect. There is no energy lost (or gained) and the process continues forever. But...there is friction.

Now how do you state that a pendulum can continue to escape Gravity's effect?

It is gravity which causes the effect. It is gravity which gives the pendulum potential energy at the top of the swing. It is gravity which converts that potential energy to momentum as it drops.

The poster who mentioned the elliptical curve is actually on target.

IF you could reduce friction to near zero and reuce the issues of pressure and a molten core to the earth you could make the experiment work.
The path of the tunnel would need to take the rotation of the earth into account to allow the rotation to be in opposition to the trajectory on the outward bound side. The north pole to south pole route would be useless but any continent to opposing continent route should work.
In addition, the elliptical curve would have to use centrifugal force to increase the speed of the elevator. They use this principle to speed up space probes by zipping them around the moon or other planets using centrifugal force. The path of the tunnel would go around the center of the planet. Not through it.

The real issue is that the same tunnel cannot be used for a return trip to the same point on the earth. A second tunnel using a different path would need to be used.

reply to post by Phage

Actually...you have just proved my point. You see...by describing Gravity as the source of Momentum and Energy...you made one FATAL FLAW in you description which proves my statements.

You describe how the Pendulum swinging as being caused by Gravity...but in order for the Pendulum to be able to swing...a FORCE MUST FIRST LIFT THE PENDULUM TO THE VERY END OF IT'S SWING OR THE FULL EXTENT OF DISTANCE BOTH HORIZONTAL AND VERTICAL FROM IT'S HANGING 6 O'CLOCK OR 180 DEGREE ANGLE OF HANG WITH 0 OR 360 DEGREES BEING STRAIGHT UP PLUMB OR 12 O'CLOCK POSITION OF IT''S HANGING POINT WHICH IS PERPENDICULAR TO THE EARTHS SURFACE.

Without this lifting force whether it be a wench or a persons hand pulling or pushing the Pendulum's weighted end the distance both Horizontal and Vertical as the distance to the Earth's Surface to the End Point of the Pendulum's Weighted Line or Wire or if you will...Steel Beam....will be closer to the Earth's surface at the 180 Degree or 6 O'clock position as apposed to the Pendulum's weighted End Point being FURTHER AWAY FROM THE SURFACE OF THE EARTH at the extent or end point or furthest point away from Perpendicular to the Earth at the END OF IT'S SWING.

This is proof that the Pendulum must be FORCED INTO MOTION. Gravity will not SPONTANEOUSLY move the Pendulum in a Perpendicular STATE OF REST...into motion. The Pendulum must FIRST BE ACTED UPON BY A FORCE THAT WILL PULL OR PUSH THE PENDULUM'S END WEIGHT TO THE FURTHEST POINT OF IT'S SWING.

EVEN IN A VACUUM AND A THEORETICAL FRICTION LESS PENDULUM....THE RELEASE POINT OF IT'S BEGINNING DISTANCE WILL NEVER AGAIN BE ACHIEVED IN ANY SWING AS GRAVITY WILL EFFECT IT AND THE VERY FIRST RELEASE WILL PASS PERPENDICULAR AND NOT ACHIEVE THE SAME DISTANCE OF HEIGHT OR HORIZONTAL DISTANCE. THIS IS FACT!
Split Infinity

reply to post by SplitInfinity

FORCE MUST FIRST LIFT THE PENDULUM TO THE VERY END OF IT'S SWING OR THE FULL EXTENT OF DISTANCE BOTH HORIZONTAL AND VERTICAL FROM IT'S HANGING 6 O'CLOCK OR 180 DEGREE ANGLE OF HANG WITH 0 OR 360 DEGREES BEING STRAIGHT UP PLUMB OR 12 O'CLOCK POSITION OF IT''S HANGING POINT WHICH IS PERPENDICULAR TO THE EARTHS SURFACE.

Of course it does. Otherwise nothing will happen at all. But once started it will continue to swing. The initial energy applied to lift the pendulum will be conserved. You claimed that a swinging pendulum would stop because of the force of gravity. You said it was swinging. That means force was applied to make it start swinging.

THE RELEASE POINT OF IT'S BEGINNING DISTANCE WILL NEVER AGAIN BE ACHIEVED IN ANY SWING AS GRAVITY WILL EFFECT IT AND THE VERY FIRST RELEASE WILL PASS PERPENDICULAR AND NOT ACHIEVE THE SAME DISTANCE OF HEIGHT OR HORIZONTAL DISTANCE.

In the absence of friction it will reach it's beginning height because there is no loss of energy.

Is it really necessary to yell?

reply to post by Phage

There is loss of energy! Every swing travels a shorter distance as it is forced to contend with Gravity.

Again I ask you...how can you account for the effect of Gravity not slowing the upswing of the Pendulum?
Split Infinity

reply to post by SplitInfinity

There is loss of energy! Every swing travels a shorter distance as it is forced to contend with Gravity.

The swings get smaller because of friction. Gravity does not extract energy from the system.

Again I ask you...how can you account for the effect of Gravity not slowing the upswing of the Pendulum?

I answer again. Gravity converts the momentum of the pendulum into potential energy.

Originally posted by Phage
reply to post by SplitInfinity

 

There is loss of energy! Every swing travels a shorter distance as it is forced to contend with Gravity.

The swings get smaller because of friction. Gravity does not extract energy from the system.

Again I ask you...how can you account for the effect of Gravity not slowing the upswing of the Pendulum?

I answer again. Gravity converts the momentum of the pendulum into potential energy.

I have stated that even in a complete Theoretical Non-Friction Environment as well as in a TOTAL VACUUM...GRAVITY will effect the Pendulum's swing and slow it to an eventual stop.

What you have stated goes against the rules of THERMODYNAMICS....how do you account for this?
Split Infinity

reply to post by SplitInfinity

I have stated that even in a complete Theoretical Non-Friction Environment as well as in a TOTAL VACUUM...GRAVITY will effect the Pendulum's swing and slow it to an eventual stop.

Yes. I know you did.

What you have stated goes against the rules of THERMODYNAMICS....how do you account for this?
Split Infinity

All of them? What I have been trying to explain is actually a very nice demonstration of first law which consists of three principles.

1) Energy can neither be created nor destroyed. No energy is being created. No energy is being destroyed. Energy is being converted back and forth between kinetic energy (momentum) and potential energy.

2) Since there is no friction, there is no heat being removed from the system.

3) Since there is no friction the only work being performed is raising the pendulum to the apex of its swing. This work is an energy transfer. All of the kinetic energy of the rising pendulum is converted into gravitational potential energy.

Perhaps you can explain where the energy is going if it is being lost. Perhaps you can explain how the other three laws (including the zeroth) are being violated.

reply to post by SplitInfinity

Gravity is a conservative force. This means momentum and energy are conserved. Gravity is not friction it can not "slow down" things else all planetary/stellar orbits would collapse immediately. This is basic physics.

You can verify it by yourself by deriving the force equation(volume integral over a sphere) and integrating over the closed path of the moving(oscillating) mass. The net work will be zero.

reply to post by Phage


So you understand that the acceleration would decrease, but you don't understand that the velocity would decrease as well? The mass above the train would convert the kinetic energy of the train back into gravitational potential energy significantly before it even reaches the center. There would hardly be enough kinetic energy in the train to pass the center by any significant amount.

The center of the Earth, and the center of this gravity train track, would have a significant near equal gravitational pull in ALL directions. Not just an equal pull vertically, but also horizontally, and all directions between, which is a very significant thing to take into account. Every time this gravity train reaches the center, the train wants to be pulled in all directions which would convert part of the train's kinetic energy into gravitational potential energy that can never be used because it is fixed on a vertical track.

Comparing a gravity train to a pendulum is highly misleading, because pendulums deal with a vertical gravitational pull only. Add a horizontal gravitational pull to a pendulum and watch it come to rest in equilibrium in the center.

Originally posted by moebius
reply to post by SplitInfinity

 

Gravity is not friction it can not "slow down" things else all planetary/stellar orbits would collapse immediately.

Really, so when you throw a ball vertically into the air, gravity doesn't "slow down" its ascension? It doesn't convert kinetic energy into gravitational potential energy?

reply to post by illuminated0ne

I guess you have overlooked the quotation marks? The "slow down" was meant in the context of friction, reducing the momentum and energy of the object. Try harder next time. LOL.

Edit:
Btw. have you eventually had time to derive the force equation?

100% behind everything Phage posted last night after I went to bed

reply to post by moebius


You claimed gravity can not slow down things. I was just correcting your erroneous claim.

B.T.W. You ignored my last reply to you.

Originally posted by illuminated0ne
reply to post by moebius

 

You claimed gravity can not slow down things. I was just correcting your erroneous claim.

B.T.W. You ignored my last reply to you.

There us a little confusion going on,
In balistics gravity can be a retardive force if the direction of motion is opposite the gravity force vector. In orbital mechanics gravity is always an accelerative force, always adding velocity to an objects motion as it spirals into the gravity well.
You are both right and both wrong

The original premise is an impossible scenario anyway,
First you couldn't have a tunnel through the center of the earth seeing as how the inner and outer cores rotate in opossition to each otherhow could you peirce the boundry if it is in constant motion.
Second, the earth rotates on its own axis and is not of uniform density either with respect to overall composition or with respect of density as compared to depth the earth gets denser the deeper you go.
As the earth rotates the areas of differing density would pull laterally on the falling mass changing its path into orbital motion.
In the simplest form a frictionless system the mass would continue to oscillate indefinitely from one end to Tue other, because as it has been.beaten to death, energy must be conserved. All of the gravitational potential energy is converted to kinetic energy and back.

reply to post by illuminated0ne

So you understand that the acceleration would decrease, but you don't understand that the velocity would decrease as well?

No, I don't understand.
The ball will continue to accelerate toward the region of greater mass. As it accelerates toward the center the mass in that direction becomes less and the mass opposite that direction becomes greater so the acceleration decreases but it is still in the same direction. Until the reaching the center, then the region of greater mass is "above" (toward the starting location) and the direction of acceleration reverses. Until the ball reaches the center there is nothing to cause it to lose velocity.

Originally posted by SplitInfinity
reply to post by Phage

 

Actually...you have just proved my point. You see...by describing Gravity as the source of Momentum and Energy...you made one FATAL FLAW in you description which proves my statements.

You describe how the Pendulum swinging as being caused by Gravity...but in order for the Pendulum to be able to swing...a FORCE MUST FIRST LIFT THE PENDULUM TO THE VERY END OF IT'S SWING OR THE FULL EXTENT OF DISTANCE BOTH HORIZONTAL AND VERTICAL FROM IT'S HANGING 6 O'CLOCK OR 180 DEGREE ANGLE OF HANG WITH 0 OR 360 DEGREES BEING STRAIGHT UP PLUMB OR 12 O'CLOCK POSITION OF IT''S HANGING POINT WHICH IS PERPENDICULAR TO THE EARTHS SURFACE.

Without this lifting force whether it be a wench or a persons hand pulling or pushing the Pendulum's weighted end the distance both Horizontal and Vertical as the distance to the Earth's Surface to the End Point of the Pendulum's Weighted Line or Wire or if you will...Steel Beam....will be closer to the Earth's surface at the 180 Degree or 6 O'clock position as apposed to the Pendulum's weighted End Point being FURTHER AWAY FROM THE SURFACE OF THE EARTH at the extent or end point or furthest point away from Perpendicular to the Earth at the END OF IT'S SWING.

This is proof that the Pendulum must be FORCED INTO MOTION. Gravity will not SPONTANEOUSLY move the Pendulum in a Perpendicular STATE OF REST...into motion. The Pendulum must FIRST BE ACTED UPON BY A FORCE THAT WILL PULL OR PUSH THE PENDULUM'S END WEIGHT TO THE FURTHEST POINT OF IT'S SWING.

EVEN IN A VACUUM AND A THEORETICAL FRICTION LESS PENDULUM....THE RELEASE POINT OF IT'S BEGINNING DISTANCE WILL NEVER AGAIN BE ACHIEVED IN ANY SWING AS GRAVITY WILL EFFECT IT AND THE VERY FIRST RELEASE WILL PASS PERPENDICULAR AND NOT ACHIEVE THE SAME DISTANCE OF HEIGHT OR HORIZONTAL DISTANCE. THIS IS FACT!
Split Infinity

Phage is right.

It would be un-damped simple harmonic motion.

At the North Pole, where the 10kg mass is released, the force is all in potential energy and the initial velocity is zero.

Falling towards the center of mass, the object accelerates and the velocity increases. The potential energy is being converted into momentum.

Crossing the center point (the center of the Earth), its velocity is at its greatest, but it won't suddenly stop because the momentum of the object is also at its greatest and will carry it on "upwards" towards the South Pole.

As the entire process is loss-less (frictionless), the object will continue to rise until velocity goes to 0 and the potential energy EXACTLY equals what it was at the start. This is also exactly the same height that it was from the center of the Earth towards the North Pole, only this time, it is towards the South Pole.

The whole process would be repeated going back the other way and since there are no losses in our imaginary scenario, the oscillation would continue forever.

Of course in the real world, if such an experiment were technically or fiscally feasible, there would be frictional losses because we cannot make a perfect vacuum. There are also likely to be magnetic frictional forces (Hysteresis) and while the start point of the 10kg mass was in orbit with the Earth and would therefore track with the Earth's orbit, there would be issues of the mass hitting the sides of the tube (producing friction) due to precession (Coriolis effect).

But Gravitation is not lossy and so the oscillation, in our perfectly frictionless imagined scenario, would be perpetual.