1N Force and going near the speed of light?

[Arman777]

Lets suppose we are in a space and there's no external force that affects our system,which our system is simply one object which we can think it is a box and it has 1 kg mass and there is us.

The object ,lets call it A,Its initally rest relative to us so it can be our inertial referance frame So We pushed the A and we applied a force to the A ( Let's call it 1N).It started to accelerate.(I am not sure at this point A will be still our inertial referance frame or not).

In this case we are observer and we will think we are stationary so the A will start to accelerate with constant acceleration $\vec F=m \vec a$ (The motion is only in one direction like +x) so, $F=1N$ and $m=1kg$ so $a=1\frac m s^2$

We know that there's no external force affecting our system.So after some time the objects speed will increase.And after a period we will use relativity theories to calculate A 's speed.The thing is I just wanted know In this circumtances , With $1N$ force object can reach $0.9999999...c$ if its given enough time ?

If you also give an answer to the question that I wrote in bold I'll happy,

Thank you

 

[oz93666]

You say ... "We pushed the A and we applied a force to the A " well that makes it accelerate away from you , so how are you going to continue to apply a force ??

But if you could find a way of applying a 1N force to a 1kg mass ... then yes , in theory you could get it to 0.9999999 c

 

[Merlin3189]

I don't think A can be an inertial frame of reference, as it is accelerating.

Since you say, we think we are stationary observer, then you are defining yourself, the observer as the frame of reference. Since you are applying the force to A, then A is applying an equal and opposite force to you (Newton's 3rd law) and you are also accelerating. So you also are not an inertial reference and neither can be any other frame in which you are stationary.

 

[Arman777]

You say ... "We pushed the A and we applied a force to the A " well that makes it accelerate away from you , so how are you going to continue to apply a force ??

But if you could find a way of applying a 1N force to a 1kg mass ... then yes , in theory you could get it to 0.9999999 c

Well It gained some acceleration right.there's no external force so it will keep its state of motion.It will accelerate with constant $a$.I don't need to apply force constantly.
Thats my idea

 

[Merlin3189]

... it will keep its state of motion.It will accelerate with constant $a$.I don't need to apply force constantly.
Thats my idea

Keeping it's state of motion, means no acceleration: constant velocity.
If you want acceleration, a force needs to be applied. $a=\frac{F}{m}$ if the force is 0, so is the acceleration.

 

[ZapperZ]

Well It gained some acceleration right.there's no external force so it will keep its state of motion.It will accelerate with constant $a$.I don't need to apply force constantly.
Thats my idea

Your "idea" is wrong. When there's no longer an applied force, it will not accelerate (Newton's First Law).

Zz.

 

[Arman777]

Ok I got it thanks.I also understand the referance frame case thanks for that too.It will accelerate and gain some velocity (lets call it v) but when I cut force there will be no acceleration so it will move with a constant velocity v.
For referance frame.A cannot be an inertial referance frame cause its accelerates.We need constant velocity object to choose an inertial referance frame.

 

[russ_watters]

But if you could find a way of applying a 1N force to a 1kg mass ... then yes , in theory you could get it to 0.9999999 c

...but you cannot get to 99.999...C

 

[Arman777]

...but you cannot get to 99.999...C

İs it some kinda of joke .I didnt understand

 

[A.T.]

...but you cannot get to 99.999...C

Not even to 0.999... c

 

[Arman777]

sure we need huge energy a lot of energy.Even for an atom we need huge amount of energy for a 1 kg object we need a lot

 

[russ_watters]

Not even to 0.999... c

Oops, lol.

 

[russ_watters]

İs it some kinda of joke .I didnt understand

Badly played joke. In math language, 0.999...=1 and since you can't go C, you can't go 0.999...C either.

 

[mfb]

Accelerating 1 kg to 99.99% the speed of light needs 6*10¹⁸ J, about the world energy consumption of a week.
Accelerating a proton to 99.99% the speed of light needs a large accelerator. The SPS and the LHC, Tevatron (and its preaccelerator), HERA and RHIC can/could do that. The energy per proton is tiny - 0.01 microjoule - but getting that energy per proton is not easy.

Accelerating a proton (well, actually 6*10¹⁴ protons) to 99.9999990% the speed of light (1.06 microjoule per proton, 600 MJ in total) is done at the LHC, it is the current record for accelerators.

 

[oz93666]

Accelerating 1 kg to 99.99% the speed of light needs 6*10¹⁸ J, about the world energy consumption of a week.
Accelerating a proton to 99.99% the speed of light needs a large accelerator. The SPS and the LHC, Tevatron (and its preaccelerator), HERA and RHIC can/could do that. The energy per proton is tiny - 0.01 microjoule - but getting that energy per proton is not easy.

Accelerating a proton (well, actually 6*10¹⁴ protons) to 99.9999990% the speed of light (1.06 microjoule per proton, 600 MJ in total) is done at the LHC, it is the current record for accelerators.

You're figures are way off mfb ... at .9999c mass is 10 tonnes needs 4.5 * 10 ^20 J...

but at 0.9999999 c the original 1kg mass would be so much greater ...trillions of tonnes I would guess...

 

[weirdoguy]

but at 0.9999999 c the original 1kg mass would be so much greater

No, read this:
https://www.physicsforums.com/insights/what-is-relativistic-mass-and-why-it-is-not-used-much/

 

[oz93666]

No, read this:
https://www.physicsforums.com/insights/what-is-relativistic-mass-and-why-it-is-not-used-much/

So are you saying the 1kg mass at 0.9999999c would not be "so much greater in mass"?
Are you saying the equation in post 15 is not valid?
If so , what is the mass at 0.9999999c?

 

[weirdoguy]

1kg. Read again the article that I gave you.

 

[oz93666]

1kg. Read again the article that I gave you.

Perhaps you can explain it to me ...I don't understand it.

 

[ZapperZ]

Perhaps you can explain it to me ...I don't understand it.

It looks like we are back on this issue again.

There's nothing wrong with the equation. It is the "concept" of "relativistic mass" that is the issue. Please note that even the "originator" of this idea of relativistic mass, Albert Einstein, stopped using it after he realized that this might be problematic. Read this post as well as that Insight article:

https://www.physicsforums.com/threads/relativistic-mass.642188/#post-4106101

Zz.

 

[oz93666]

It looks like we are back on this issue again.

There's nothing wrong with the equation. It is the "concept" of "relativistic mass" that is the issue. Please note that even the "originator" of this idea of relativistic mass, Albert Einstein, stopped using it after he realized that this might be problematic. Read this post as well as that Insight article:

https://www.physicsforums.com/threads/relativistic-mass.642188/#post-4106101

Zz.

So if there's nothing wrong with the equation , the mass would be 10 tonnes at 0.9999c , and trillions of tonnes at 0.9999999c , is that right?

 

[ZapperZ]

So if there's nothing wrong with the equation , the mass would be 10 tonnes at 0.9999c , and trillions of tonnes at 0.9999999c , is that right?

There's nothing wrong with A LOT of equations. For example, in the simple kinetic energy equation

KE = 1/2 mv²

I can also write it as (m/2)v². Someone may wish to interpret it as having only HALF of the mass having the kinetic energy, while the other half doesn't! Can't you see how this makes it sound absurd?

The same applies to relativistic physics. You are extracting a part of a larger, more general form, and then trying to "interpret" what it means. Simply look at how that form is derived, and you'll see that what is "primary" here (as used in one of the papers I cited) is "relativistic MOMENTUM" and "relativistic ENERGY". The "mass" can and should only be defined as the inertial or invariant mass.

Please note that in high energy physics, where a lot of particles are zooming around at relativistic speeds, if you look in the Particle Data book on their masses, they NEVER cite masses at specific speeds.

Zz.

 

[oz93666]

My understanding is this has all been verified in particle accelerators up to 0.9999999c and beyond ?

There's nothing wrong with A LOT of equations. For example, in the simple kinetic energy equation

KE = 1/2 mv²

I can also write it as (m/2)v². Someone may wish to interpret it as having only HALF of the mass having the kinetic energy, while the other half doesn't! Can't you see how this makes it sound absurd?

Honestly I can't ... this ke formula is very clear and works ...

Please tell me how I find the the mass of 1kg rest mass object at 0.9999c

 

[Arman777]

My understanding is this has all been verified in particle accelerators up to 0.9999999c and beyond ?Honestly I can't ... this ke formula is very clear and works ...

Please tell me how I find the the mass of 1kg rest mass object at 0.9999c

Open an another thread pls

 

[mfb]

Please tell me how I find the the mass of 1kg rest mass object at 0.9999c

It is 1 kg. Because "mass" means "invariant mass"="rest mass".
You can use the concept of a relativistic (velocity-dependent) mass, but no one does that any more.

Your factor of 1000 is wrong.

$$\gamma_{99.99\%c} = \frac 1 {\sqrt {1-0.9999^2} }= 70.71$$

$E=\gamma_{99.99\%c} 1kg~c^2 = 6.36 \cdot 10^{18} J$

Can we come back to the original topic?

 

[ZapperZ]

My understanding is this has all been verified in particle accelerators up to 0.9999999c and beyond ?

I'm an accelerator physicist, just so you know.

Secondly, we don't measure "mass". We only obtain mass based on the measurement of something else. If I send a stream of particles into a dipole magnetic field and measure the "bending" amount, what I get DIRECTLY is the MOMENTUM. It is only after applying some physics will I be able to extract the "mass" of the object.

You are exhibiting a bit of stubbornness here in the sense that you haven't shown any indication that you've read the sources you've been given. The fact that there were at least 2 different links given to you that CLEARLY indicated why the concept of "relativistic mass" can be problematic somehow appeared to have been ignored.

If you ever get into trouble later on due to your insistence of using this concept, please note THIS DAY where you have been warned.

Zz.

 

[PeroK]

Lets suppose we are in a space and there's no external force that affects our system,which our system is simply one object which we can think it is a box and it has 1 kg mass and there is us.

The object ,lets call it A,Its initally rest relative to us so it can be our inertial referance frame So We pushed the A and we applied a force to the A ( Let's call it 1N).It started to accelerate.(I am not sure at this point A will be still our inertial referance frame or not).

In this case we are observer and we will think we are stationary so the A will start to accelerate with constant acceleration $\vec F=m \vec a$ (The motion is only in one direction like +x) so, $F=1N$ and $m=1kg$ so $a=1\frac m s^2$

We know that there's no external force affecting our system.So after some time the objects speed will increase.And after a period we will use relativity theories to calculate A 's speed.The thing is I just wanted know In this circumtances , With $1N$ force object can reach $0.9999999...c$ if its given enough time ?

If you also give an answer to the question that I wrote in bold I'll happy,

Thank you

Leaving aside all the nonsense in your post and simpifying your question to:

A $1kg$ object is constantly accelerated by a $1N$ force. How long will it take to reach a speed $v$, which is close to the speed of light?

There is a very nice formula for this. If we let $\gamma = \frac{1}{\sqrt{1-v^2/c^2}}$, then

$t = \gamma \frac{mv}{F}$

This differs from the classical case, $t_c$, where $v$ is much less than the speed of light, only in the $\gamma$ factor:

$t_c = \frac{mv}{F}$

The classical time to get to a speed close to $c$ is about $10$ years (very approximately) with $m = 1kg$ and $F = 1N$

In the relativistic case, with $v= 0.99c$ we have $\gamma = 7$, hence $70$ years to get to 99% of the speed of light (as measured in the original rest frame of the particle being accelerated).

And, with $v = 0.999c$ you get $\gamma = 22$, hence $220$ years. Etc.

 

[Arman777]

A 1kg1kg1kg object is constantly accelerated by a 1N1N1N force. How long will it take to reach a speed vvv, which is close to the speed of light?

You don't need to say it nonsense and you don't need to insult that someone who doesn't know and trying to leanr..Real nonsene is I didnt ask such question.Where that came from ?

Can someone close this thread pls.It going out of topic

 

[PeroK]

You don't need to say it nonsense and you don't need to insult that someone who doesn't know and trying to leanr..

That's fair enough and I apologise. What I should have said is that most of your post is so muddled that it is difficult to answer, but it does contain an interesting question.

 

[oz93666]

It is 1 kg. Because "mass" means "invariant mass"="rest mass".
You can use the concept of a relativistic (velocity-dependent) mass, but no one does that any more.

Your factor of 1000 is wrong.

$$\gamma_{99.99\%c} = \frac 1 {\sqrt {1-0.9999^2} }= 70.71$$

$E=\gamma_{99.99\%c} 1kg~c^2 = 6.36 \cdot 10^{18} J$

Can we come back to the original topic?

My apologies mfb ...your figure is correct ...

But I still don't get this mass thing ... we seem agreed that at 0.9999c the 1kg mass now has a mass of 70kg ... I only know of one kind of mass... it pulls on other mass (gravitation) ...and resists acceleration , that's all mass does isn't it? I didn't know there were different kinds of mass and subdivisions in the term.