F=m*v or E=M*C2 Which is right for you?

[Fallingstar1971]

I have been reading about Newton and Einstein and seen these two formula........

But dont they say the same thing? Only "V" is now called a constant?

So I ask, which is right for you?

If I knew how to make it a poll, I would

Star

 

[origin]

I have been reading about Newton and Einstein and seen these two formula........

But dont they say the same thing? Only "V" is now called a constant?

So I ask, which is right for you?

If I knew how to make it a poll, I would

Star

Well the first equation is wrong, so it is clearly not 'right for me. I think you meant F=ma

And if you meant which is right F=ma or E=mc^2 the answer is both are 'right'.

 

[baulten]

You're comparing equations for two different things. Force is not the same as Energy. They're both correct.

 

[drwayne]

You seem to have mangled together equations for *momentum*

P = mv

with *force*

F = ma (for constant mass, note that this is NOT true for a rocket)

Now, force and momentum are related by the full form of a Newton relationship

F = dp/dt

i.e. the time rate of momentum change in a system is equal to the applied force.

Bottom line is that the equation

F = mv

is BADLY wrong. Not because of something Newton did, but because of something
you did.

 

[ramparts]

Yeah, someone used the equation F=mv in some thread here a couple of weeks back, and it was horribly horribly wrong.

Also, in general, physics is NOT done by poll. An equation can't be right for some people and wrong for others. Either it's right or it's wrong - end of story

 

[drwayne]

General observation:

An equation is more than a bunch of letters and an equal sign. It is a concept written in the language
of mathematics. The terms in the equation have specific physical meaning.

One can write great literature with only a superficial understanding of grammar. (See Faulkner)
You can't do math and physics that way.

Wayne

 

[benbald]

Yeah F=m*a, not F=m*v... But you're comparing apples and oranges here. Force and Energy, different things.

 

[Fallingstar1971]

I was thinking that force was another manifestation of energy. I guess its not.

O and sorry I messed up your little "letters". Im exploring physics and never said I was an expert. A simple kind correction would have been fine.

I was under the impression that the goal of physics was to fit everything together. I thought I was seeing two sides of the same coin.

Dont take it personally and get offensive. The guy that first described the Atom committed suicide because he took it so personally.

Star

 

[ramparts]

Wow! Touchy! I just re-read the responses here and they seem pretty reasonable, fallingstar, no one being "unkind" or making fun of you or anything. I think "your little 'letters'" is by far the most combative thing said in this thread so far

Anyway, yeah, F=ma and E=mc^2 aren't two different sides of the same coin. They're both physics equations which are generally true (within their domains of applicability). F=ma tells you the relationship between force, mass, and acceleration - so if you apply a force to an object of a given mass, you know how much it'll accelerate. E=mc^2 relates an object's rest mass to the energy that it carries internally (it's so-called rest energy). Different things, but both right.

 

[MeteorWayne]

One can't just throw out formula without at least understanding what the variables represent in the Physics forum. If you don't know what the letters stand for, then Physics is not the right place to post such an idea. This is a hard science forum. The sarcastic use of "letters" in quotes as if that's nitpicking is not justifiable. In physics, the "letters" have very specific meanings.

If you don't know what the letters represent, then The Unexplained is the correct place, because that is where the discussion will wind up.

 

[drwayne]

Well, the poster at least gets credit for showing back up after a math mistake was pointed out.
The person that started with

F = mv^2

and tried to act cool by throwing around Einstein's first name just abandoned the thread when his
mistakes were pointed out.

Wayne

 

[Fallingstar1971]

No wayne, I have a real job and just cant troll the forums all day........

And again, I apologize for messing up your formula. I mis-understood

But we can go round and round all you like. Again, I am not a physics major, just someone trying to learn. I thought I saw a connection. But obviously I was MISTAKEN.

I AM TRYING TO LEARN, IF YOU ARE NOT WILLING TO TEACH, THEN STAND DOWN AND LET A MODERATOR ON WHO CAN!

Abandoned the thread INDEED!

Star

 

[drwayne]

Re-read what I wrote. I indicated that you got credit for reappearing in CONTRAST
to ANOTHER user making a very similar point with a different wrong formula. It
was the other poster who simply abandoned the thread.

And I did explain what you got wrong, and what the correct relationship were.
Your response was simply to get angry about getting the "letters" wrong.

Wayne

p.s. There are two people named Wayne in this thread.

 

[darkmatter4brains]

If you don't know what the letters stand for, then Physics is not the right place to post such an idea.

Wayne, I personally think you guys at SDC are expecting a little too much from an Internet forum. If ppl cant come here and ask questions, make misakes and learn, where can they go??

This is a hard science forum.

:lol: :lol:

that one cracks me up every time

 

[MeteorWayne]

Well then you misunderstand the purpose of the Physics forum.

 

[darkmatter4brains]

Well then you misunderstand the purpose of the Physics forum.

Well, I think I understood the purpose, I'm just saying its gonna be hard to acheive, I think.

The SDC home page, in my mind, is geared up as a "popular" space-type-interest site intended for the masses. Whether or not it is intended to be, I think it sure seems to be just that. Those same "masses" are going to leak into the forums. That means you're going to have people of all levels and background posting on here and, well, maybe you won't get the most scientific based questions some times.

So, you can either welcome the posts and help people learn, or try to stick by this whole "hard-science" forum stance, which doesn't even match reality, and wage the never-ending battle you guys seem to be caught in.

This is just my personal opinion and feel free to ignore me. Most people do. ;-) I just think it would make SDC a much friendlier place for people coming here to learn.

 

[TechMom]

I have been reading about Newton and Einstein and seen these two formula........

But dont they say the same thing? Only "V" is now called a constant?

So I ask, which is right for you?

If I knew how to make it a poll, I would

Star

The first equation is not correct - I believe you're asking a question about force (mass*acceleration) and Energy. These are two separate concepts and not comparable. I need to look through the threads to see how others have replied. But, you've inspired me to come up with some questions like this for stumping my students at the lunch table. I work with high school kids at a /*Advertizing Link Removed */ and they love these kinds of questions - and I like to see is they catch errors like this.