Acceleration and mass

[jajrussel]

If something is moving at a constant velocity say 10 kilometers per second, and is said to have a specific mass. Then accelerates to 20 kilometers power second, there is a mass gain due to acceleration? And, or due to what accelerated it?

 

If no other force acts on it will it continue accelerating? Or is continued acceleration limited by the initial force that caused it to accelerate?

 

By accelerate in these questions I mean continue to gain velocity.

[studiot]

You first need to decide whether you are looking at this clasically or via special relativity.

 

You have talked of mass, acceleration and velocity in a classical manner but asked if there is a relativistic mass increase.

 

Please don't mix analysis methods.

 

Edit have you looked at my answer to your other new thread?

Edited September 20, 2015 by studiot

[jajrussel]

You first need to decide whether you are looking at this clasically or via special relativity.

 

You have talked of mass, acceleration and velocity in a classical manner but asked if there is a relativistic mass increase.

 

Please don't mix analysis methods.

 

Edit have you looked at my answer to your other new thread?

In the other thread you cleared up some of my wrong thinking, and gave me new things to consider. Thank you.

 

In this thread I didn't realize I was overlapping analysis methods. Though the thought occurred to me that Newton wise (that if a thing is moving at a constant velocity, unless a force acts on it, it will continue to do so.) Could the same be said for a thing that is accelerating? It doesn't seem that big a leap if no force is acting to stop it, which is why I was wondering if there was a limiting factor in the initial force that caused the thing to accelerate to only a limited degree. Why would it stop accelerating? I confess that it was thinking about Newton mechanics, and Einstein's transfer to relativity that brought the question. Though I have the impression that it was the mention of mass gain that split my analysis methods for you?

Edited September 20, 2015 by jajrussel

[swansont]

If something is moving at a constant velocity say 10 kilometers per second, and is said to have a specific mass. Then accelerates to 20 kilometers power second, there is a mass gain due to acceleration? And, or due to what accelerated it?

 

If no other force acts on it will it continue accelerating? Or is continued acceleration limited by the initial force that caused it to accelerate?

 

By accelerate in these questions I mean continue to gain velocity.

 

 

Once the force ceases, the acceleration ceases.

 

There is no mass gain. (Unless you redefine what you mean by mass)

[studiot]

 

I confess that it was thinking about Newton mechanics, and Einstein's transfer to relativity that brought the question. Though I have the impression that it was the mention of mass gain that split my analysis methods for you?

 

 

20km/s is not really fast compared to the speed of light so why did you mention mass gain?

 

There is no mass gain, regardless of speed or acceleration under classical (Newtonian) mechanics.

 

The object will only accelerate whilst there is a force acting on it.

 

Remember that a deceleration is considered as a negative acceleration and that change of direction without change of speed is also an acceleration.

 

There is further information in your other post.

 

So to recap, this is a discussion in classical mechanics, perhaps about a meteor or asteroid?

[jajrussel]

I was thinking about anything that shows mass be it asteroid, meteor, or particle. With due consideration to c, as a limiting factor. Though my thoughts dealing with 0 mass particles are not clear to me because I an not sure what to think about them. They seem to exhibit mass, and it is as if they have two states, one of existence, and one of none existence. When they exist they move at c, but can have different energy levels, which seems to present mass which I am assuming would be determined by its energy.

 

My other assumtion is based on the question, what is a photon, or any other 0 mass particle at rest, if not non existent? I am not sure this thought is right?

 

Another question is about photon interaction, when it directly interacts is it absorbed causing a change that emits another photon with perhaps a different energy level,or is the photon that allows me to see the tree in the yard here actually reflected light?

 

I guess if I drew a line between classical mechanics, and relativity I would probably get its exact placement wrong, because I thought mass gain due to acceleration was relevant to both.

[jajrussel]

 

 

Once the force ceases, the acceleration ceases.

 

There is no mass gain. (Unless you redefine what you mean by mass)

I am wondering that if it takes force to effect a change in velocity, which we can call acceleration in any form you prefer, why doesn't it take force to change the effect? Any change seems to always be dependant on force.

 

I am sorry, I was not aware that I had defined mass. I do have trouble understanding terms sometimes, but my assumtion is, now that I know a distinction must be made, my meaning should likely be a relative one since I was implying a mass gain through an increase in velocity. At least that is what I thought I was saying. I do admit that, I now accept that in classical mechanics there is no mass gain, but I also have to admit that from a relative point of view that I don't know how that is possible.

Edited September 20, 2015 by jajrussel

[swansont]

I am wondering that if it takes force to effect a change in velocity, which we can call acceleration in any form you prefer, why doesn't it take force to change the effect? Any change seems to always be dependant on force.

 

 

Removing a force is the same as adding a force that cancels it.

[jajrussel]

 

Removing a force is the same as adding a force that cancels it.

Okay.

 

Is there an inertia gain?

[swansont]

Okay.

 

Is there an inertia gain?

 

No.

[jajrussel]

I have been reading about the difference between weight and mass. It is somewhat confusing. If on earth if I weigh 80 kg how do I translate that to mass?

 

On the moon I would weigh less, but the mass remains the same. There is a difference in acceleration, but in terms of energy I am the same?

[Endy0816]

Kilograms is a unit of mass.

 

If your mass is 80 kg on Earth, it will be 80 kg on the moon.

 

The force you feel as a result of gravity(weight) is what will be less on the moon.

[studiot]

Actually jaj russel asked about kg weight (which is a unit of weight).

 

Weight is the force of gravity exerted on a mass so is a force.

 

Force = mass x acceleration

 

So if we rearrange this we have mass = Force / acceleration.

 

So the mass in mass units of 80kg weight is 80/g or approx 80/10 = 8 kg mass

 

https://en.wikipedia.org/wiki/Kilogram-force

[Endy0816]

Actually jaj russel asked about kg weight (which is a unit of weight).

 

Weight is the force of gravity exerted on a mass so is a force.

 

Force = mass x acceleration

 

So if we rearrange this we have mass = Force / acceleration.

 

So the mass in mass units of 80kg weight is 80/g or approx 80/10 = 8 kg mass

 

https://en.wikipedia.org/wiki/Kilogram-force

 

Newton gets no love.

[swansont]

Actually jaj russel asked about kg weight (which is a unit of weight).

 

This is in physics and we try to use SI units.

 

From the link:

"Kilogram-force is a non-standard unit and does not comply with the SI Metric System"

[jajrussel]

Studiot was right. My reference was to weight. The equation helped to clear up my thinking because the article I read was showing two different equations. When I tried to derive the answer I got two different results one was large one was small. The large answer seemed to be wrong, but I wasn't sure.

 

The reply showed me that the smaller answer was correct, it wasn't that difficult to realize that the 9.8 had beenrounded off to 10.

 

Endy0816's answer did not confuse me,but it did make me smile, actually both times.

 

I have read that even physics people forget that SI rules on occasion.

 

I have also read that physics people on occasion will insist on using SI units even when it is clear that the person they are addressing is clearly confused because they are not.

 

One of the things that confused me was the use of kg for both mass, and weight. Can I assume that some of us English using pounders are not the only ones guilty of confusing a decent physicist by not bothering to learn the language before we attempt a conversation?

 

I'm only joking here. Sort of. Kind of.

 

If we pounders, and Europeans were to refer to weight that is not given in pounds, is there a correct SI unit? And, if I were to start using it, would the metric people admit to knowing what I was talking about.

 

My ex wife could have been a scientist,she hated the word weight. Actually, I hated even approaching the word. Had I used the word mass she would likely now be a widow, rather than my ex wife.

Edited September 28, 2015 by jajrussel

[swansont]

Studiot was right. My reference was to weight.

 

In physics, weight is a force and measured in Newtons. If you use kg it means mass. That way we avoid this sort of confusion.

[jajrussel]

Thanks.

[Endy0816]

I don't recall if the usage of kg or kgf as a unit of force was even mentioned in our equivalent of secondary.

 

I suspect it is just easier to teach 1N=1kg * 1m/s^2 and leave discussion on what units people more commonly use aside