# Relativistic effects on a body rotating at near c

• dan_r
In summary: This is due to the increase in the gravitational field around the body, which would eventually cause the body to reach a stable state at a lower velocity than the original.In summary, an apparatus could be set up to achieve a high velocity using the inertial effect, but it would require a large amount of energy to do so.
dan_r
Hi all, I've just been thinking about something today which I freely admit I've not got the knowledge to actually comprehend at this time (my physics studies don't start until September!) and so it might actually belong in engineering or it might just be a load of nonsense that I've gotten wrong!

If I were to set up an apparatus and attach a little model spaceship to it, which extended around, say 10m from the apparatus. Could I then, given the correct amount of energy input, rotate the apparatus at such a speed whereby the little model spaceship could achieve a velocity close to c.. and if so, would we start seeing relativistic effects occurring around the spaceship and apparatus as well?

So you're not actually achieving such speeds through direct velocity sending something in a straight line, but through the inertial effect on an extended body from the apparatus.. would that lower the energy demands of reaching such velocity if the extended body were constructed as to be able to withstand the rigours of such speeds?

I am not at all sure what you are asking here. The kinetic energy in an object moving at speed v is the same whether it is moving in a straight line or circle. The energy necessary to get it to that speed is the same in either situation.

Hi, sorry it is a bit unclear.

It could be better described as the level of acceleration around a pivot. In my head I'm imagining it as being almost like a lever, whereby you can generate higher velocity with a much reduced input of energy?

I'll draw a diagram when I get home to my PC; I'm terrible at trying to explain what I can see in my mind!

dan_r said:
Hi, sorry it is a bit unclear.

It could be better described as the level of acceleration around a pivot. In my head I'm imagining it as being almost like a lever, whereby you can generate higher velocity with a much reduced input of energy?

I'll draw a diagram when I get home to my PC; I'm terrible at trying to explain what I can see in my mind!

With a fixed mass, the same velocity needs the same energy. Anything else, and you could build a perpetual motion machine. But if you can, then you are a very rich man.

--the other danR

danR said:
With a fixed mass, the same velocity needs the same energy. Anything else, and you could build a perpetual motion machine. But if you can, then you are a very rich man.

--the other danR

Haha, very rich indeed! Good to see us Dan Rs get around though!

I think I'm understanding where I'm going wrong with this idea now; I was getting the impression that the inertia would drive the extended item to move at a higher velocity than the pivot around which it spun, because obviously it stays equidistant from the pivot, but covers a longer distance.

In my head I was thinking that the pivot could spin at x but the item would travel at y because of this.. it's a bit like a mental illusion I suppose. Got a lot to learn!

Well, it would have a higher angular velocity than the pivot point, you're correct there.

cowmoo32 said:
Well, it would have a higher angular velocity than the pivot point, you're correct there.

Ah good! My brain WAS working then!

Ok, with that info, I've found this thread on search which might be of interest to people who've followed the thread:

It seems that you would reach a point where the body spinning around the axis would acquire so much mass that it would start to slow down the mechanism of rotation hence slowing down itself.

## 1. What is the concept of relativity in relation to a body rotating at near c?

The concept of relativity states that the laws of physics are the same for all observers, regardless of their relative motion. This means that the effects of rotation on a body moving at near the speed of light (c) will be the same for all observers, regardless of their frame of reference.

## 2. How does the speed of rotation affect the relativistic effects on a body?

The speed of rotation has a significant impact on the relativistic effects on a body. As the speed of rotation approaches the speed of light, the effects become more pronounced and can lead to phenomena such as time dilation and length contraction.

## 3. What is the relationship between time dilation and rotation at near c?

Time dilation is a phenomenon in which time appears to pass slower for an object in motion compared to an object at rest. When a body is rotating at near the speed of light, the centrifugal forces acting on the body cause it to experience time dilation, meaning time appears to pass slower for the rotating body compared to a stationary observer.

## 4. How does the rotation of a body at near c affect its mass?

According to Einstein's theory of relativity, the mass of an object increases as its velocity approaches the speed of light. This means that a body rotating at near c will have a greater mass compared to an identical stationary body due to the effects of rotation.

## 5. Can the relativistic effects on a body rotating at near c be observed in everyday life?

No, the relativistic effects on a body rotating at near c are only significant for very high speeds, such as those approaching the speed of light. In everyday life, the effects of rotation on a body are negligible and can only be observed in highly controlled laboratory settings.

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