Figure this out for me....

[Ol Smoke]

I will try to make this as easy as I can so hang on.

 

Let's say you have an old record player.  It is spinning at 33 1/3 rpm constantly.

 

How fast is the outside groove of the record spinning ?  How fast is the inside groove spinning?

 

Okay...the answer is  33 1/3 rpms.  If it wasn't so, then the track closest to the center would be going faster,

and the song would sound like the chipmunks.

 

So with that said, answer me this.

 

If you take a wheel that is on an axle and set it on the outside track of the record, it spins at a certain speed.

If you put that wheel on the inside track, it will spin faster.

 

My question is this.  If the inside and the outside tracks are spinning at the same speed,  why doesn't the wheel turn at the same speed??

 

[Owned]

After having put some thought into it, the only thing that came to my mind would be a differense in energy transmission.

 

If you put a wheel on the inside track the distance would be shorter and thus the distance the motion energy would have to travel would be shorter and thus resulting in greater power on the output.

If it is on the outside the length the motion energy has to travel will be longer, and you guessed it, will have a lower output as more of the energy is lost due to the length it had to travel resulting in a lower amount of rmps.

 

No clue if this is correct, but i tried

[Vanaraud]

Oh .... me, wrote a long story and then closed the window:P

 

well long story put short in angular momentum linearly moving point has to increase its linear speed farther from center in order to keep kinetic energy: http://en.wikipedia.org/wiki/Moment_of_inertia

As well one could ask whats the point of Newton laws, if you´d think further it just is so and proved to hold grounds with lots and lots of experiments.

 

In quantum mechanics there could be exceptions to it: see electron tunneling for example.

 

Edit: btw rpm is constant, as rounds per minute or 360 degrees\s. The linear speed of an point is different.

[Ganja.]

LOL But the record player is hard to think about, because I mean, the closer it gets to the inside, the faster it will get back around... but that doesn't mean its going faster, it just has less to go. right?

[Scab]

My first thought is the wheel rpm would be 33 1/3 no matter where it touches the record. I have access to hand held tachometers here at work so I'll try to test.

[ajnl]

The outer side of the record has to cover more distance compared to the inner side of the record. Therefore the outer side does "move" faster.

 

The RPM on the outside/inside is the same. However the distance travel is not, therefore the velocity must be higher.

 

 

Circumference is calculated using: C = 2*pi*r

r = radius

rpm = 100/3

rps (rotation per second) = 0.5556

 

C (outer) = 2*pi*10 = 20*pi centimeters = 0.2*pi meters

C (inner) = 2*pi*5 = 10*pi centimeters = 0.1*pi meters

 

V = velocity

V (outer) = C(outer)/rps = 0.2*pi/0.5556 = 0.35997 meters/second

V (inner) = C(inner)/rps = 0.1*pi/0.5556 = 0.17799 meters/second

 

RPS is same, inner/outer

Distance traveled is two times as much, therefore velocity of the outer ring must also be two times as much.

Edited October 25, 2014 by ajnl

[Ganja.]

Lol Edison is the man

[docwarren]

 

well long story put short in angular momentum linearly moving point has to increase its linear speed farther from center in order to keep kinetic energy: http://en.wikipedia.org/wiki/Moment_of_inertia

As well one could ask whats the point of Newton laws, if you´d think further it just is so and proved to hold grounds with lots and lots of experiments.

 

 

In other words...... draw a pencil line straight across from the center to outer edge. They will both make 33 1/2 RPM at center & outer edge.

 

Man.... I hated physics in college. So much of it is common sense.

[RedBaird]

The audio-vibration-scorings on the outermost grooves are less dense than those on the innermost grooves.

Picture yourself speaking into a microphone attached to an old-style platter recorder. The disk spins at constant speed, but the needle spirals inward, loosing speed as it goes. When the record is played back, the rate of data sent to the speaker is the same as was recorded from the mike.

A wheel placed on the outer rim of the record will spin around it's axle faster than one placed nearer the spindle hole.

The record spins at 33.3 rpm, but the inner and outer grooves move at different speeds.

 

ADDED:  "loosing speed as it goes" is how a tiny observer standing on the record would view the needle's motion.  

Edited November 30, 2014 by RedBaird

[Ganja.]

The audio-vibration-scorings on the outermost grooves are less dense than those on the innermost grooves.

 

Picture yourself speaking into a microphone attached to an old-style platter recorder. The disk spins at constant speed, but the needle spirals inward, loosing speed as it goes. When the record is played back, the rate of data sent to the speaker is the same as was recorded from the mike.

 

A wheel placed on the outer rim of the record will spin around it's axle faster than one placed nearer the spindle hole.

 

The record spins at 33.3 rpm, but the inner and outer grooves move at different speeds.

I still don't think the grooves change speed, just distance, appearing to speed up or slow down depending on where the needle is. Because the needle goes all the way around to where it started quicker on the inside, it seems like its going faster. Same speed shorter distance. 

Did Edison think of all this?

[Buckwild]

When a master for vinyl records is made,  Near the outside of the disk is moving faster,

 

and slows down slowly as it gets towards the center.

 

So, The oscillations of the recording are closer together near the center.

 

With the speed at the stylus slower.

 

Thomas Edison's first phonegragh of tinfoil on a cylinder wasn't tapered, Was it?

[Ganja.]

When a master for vinyl records is made,  Near the outside of the disk is moving faster,

 

and slows down slowly as it gets towards the center.

 

So, The oscillations of the recording are speeded nearer to the center.

 

Thomas Edison's first phonegragh of tinfoil on a cylinder wasn't tapered, Was it?

Yes the foil was embossed, otherwise there would only be one sound.

[Ol Smoke]

One of the uses of this physics trait is in dynamic transmissions, used in farm and lawn mower equipment.

The "gearless" transmission in combines and riding mowers uses this phenomenon. To speed the tractor up, you move the handle to move the drive

wheel toward the center of the spinning disc.  To slow it down, you move it outward.

 

What I was confused about was the speed of the platter being constant at 33 1/3 but yet the distance around the record is different from the edge to

the center.  But here is the answer to this problem.  It is the passage of time under the needle of the record.  It doesn't matter how far it is around the

record, but the speed at which the disc passes under the needle.  Since it is constant, the recording is the same from edge to center.  If you draw a line

from the center of the LP to the edge, you can count how many times it goes around, from either location.  This is why I kinda asked this question.  When

the Earth rotates, it is the same no matter where you stand on the Earth.  Even at the North Pole it makes one turn every 24 hours.  Just as it does at the

equator.  This doesn't seem right does it?   But there is a physics law about circumference and speed and time.  Vanaraud probably knows it.

 

To get you even more confused with this.  Try this.  If a basketball player spins a basketball on his finger, does the top/bottom of the ball spin faster than

the center of the ball?  No.  But if you put a speed wheel onto the ball and measure the speed at which the ball is turning under the wheel.  It will show that

the speed changes when you move it to the top from the center.  This is because you have added another potential to the equation.  Distance.  The wheel

doesn't see the speed of the ball, it sees only the distance that is traveling under it.  Now by adding speeding up the ball, or slowing it down, you have added

another potential. Time.   Time - distance - speed= acceleration

 

This was one of the problems that Einstein used to show how time was involved in the movement between locations in the universe.  He used it to prove

his first theory of relativity.

 

So simple isn't it.  Now you know that simple things in life can lead to the most complicated theories we know.

 

 

Einstein's second theorem on space movement thru time was even more simple.  He was riding in a trolley one day and noticed how the trolley moved at one

speed while the people on the sidewalk moved at another speed, and all the while, he wasn't moving at all.  Yet he was moving through space time, the whole

time.

 

Cool huh ?   Stuff like this is so fascinating.

 

 

 

 

 

 

[Buckwild]

The distance traveled at the outer edge of the record is greater.

 

But It was recorded with the record spinning, And will playback how it was recorded.

 

The speed at the stylus is slowing constantly but so it was while recording.

[Vanaraud]

A|---------------|B, if you twist the A to the B you get a circle, and to move from point A to point B in time T one has to move in linear speed V. RPM being constant means one turn from A to B being made in certain time: 33 turns per minute-> 1 turn with 1\33 minute.

As to the outer side of the disk the distance from A to B=s grows, but time is the same, from v=s\T one can see that the greater the s=AB, the greater the v has to be. Thats why there is separeted angular speed f\t(rpm) and linear speed for a point on the disk with distance A to B.

 

Now you can imagine that the needle is staying put and the bumps on A to B are passing by under the needle. As in outer side of the disk the linear velocity is greater, the bumps are passing by faster and vice versa. So you´d have to adjust the recording speed on the disk accordingly so it didn´t play the track on different speeds on different locations.

 

As to why its so. I came up with this explanation. Imagine a axe standing on ground perpendicular to the ground(90 degrees). Now if one would attach longer "stick" to the axe the potential energy grows: Ep= mgh, m being mass, g acceleration from gravity, h height from earth. As m and g being constant(in 3 dimensional Eukleidian room on sub light speeds;)) on earth and the potential energy has to go from max to 0(at the point axe lands earth when falling down) the kinetic energy has to be greater the greater the h or r(=s\f) in the case of angular movement. Ek= (mvˇ2)\2 and  while m being constant and Ek growing the v, as linear speed, has to grow. In the process axe draws a trajectory quarter of circle by falling down .

The law of conservation of energy grants that Ep transforms to Ek, which holds grounds for 60-70y now? And thats in classical mechanics, there was a post about it earlier in forums.

 

Sorry for the long post but had to sharpen my pencil as it has been too long from it and it seemed some didn´t quite get it... So hope it helped a bit.