Quick physics question

[Popcorn Sutton]

Why is energy equal to mass times the speed of light squared? It doesn't make sense to me. Why squared? Why the speed of light?

[idontknowwhyijustknow]

i agree science has many fallacies as good as it is

real amatuer

 

the speed of light i presume because it is the main source of energy ,when referring to acceleration you are referring to a force

as for why squared dunno evrything seems to get squared lol

as for mass personally i think they measure it incorrectly but thats another story

[pzkpfw]

i agree science has many fallacies as good as it is

real amatuer

 

the speed of light i presume because it is the main source of energy ,when referring to acceleration you are referring to a force

as for why squared dunno evrything seems to get squared lol

as for mass personally i think they measure it incorrectly but thats another story

 

I'll leave someone else to answer the OP (the full derivation is beyond me to explain), but to this I'd say - not understanding something does not make that thing "wrong".

 

The energy-mass equivalence is derived from known principles and has been tested. These things are not just plucked out of the air and agreed to by scientists because they like each others shoes.

[Sensei]

i agree science has many fallacies as good as it is

real amatuer

 

the speed of light i presume because it is the main source of energy ,when referring to acceleration you are referring to a force

as for why squared dunno evrything seems to get squared lol

as for mass personally i think they measure it incorrectly but thats another story

 

Learn how to calculate Decay Energy of isotope.

 

It's showing how mass changes to energy in decaying unstable isotope.

Newly produced particles are accelerated to very high speed and escaping parent element.

 

As your knowledge seems to be very rough, I will show you video how radioactive decay looks like:

 

 

https://www.youtube.com/watch?v=ZLiXgdymIYE

 

Long thin traces are the most likely from electrons (you can check it by placing magnet or electromagnet and observing bending of trace).

 

Short thick traces are from alpha particle.

 

The longer trace, the more energy had particle.

 

 

https://www.youtube.com/watch?v=VFVZU2YwwJ4

Edited April 9, 2014 by Sensei

[ajb]

Why is energy equal to mass times the speed of light squared? It doesn't make sense to me. Why squared? Why the speed of light?

Well the fact that the units of energy are equal to the units of mass times the units of velocity squared tells you that it could not simply be velocity or velocity cubed, unless you introduce some more physical constants to take care of the units.

 

The reason why it is simply E=mc^2 and c comes from special relativity. Einstein's original argument uses conservation of energy when a body emits photons. I am sure you can find some description of this somewhere.

[davidivad]

Here’s the idea; energy is distance times force (E=DF), and force is mass times acceleration (E=DMA), and acceleration is velocity over time, which is the same as distance over time squared (E = DMD/T² = MD²/T²).

So energy has units of mass times velocity squared. So, if there were some kind of universal relationship between mass and energy, then it should depend on universal constants. Quick! Name a universal speed! E=MC²

 

http://www.askamathematician.com/2011/03/q-why-does-emc2/

[ajb]

So energy has units of mass times velocity squared. So, if there were some kind of universal relationship between mass and energy, then it should depend on universal constants. Quick! Name a universal speed! E=MC²

Okay, just as I said the units work out, but [math]E = \lambda \: mc^{2}[/math] for any number [math]\lambda[/math] also works based just on units. The correct numerical factor requires some calculation. But okay, this is the simplest it could be based just on your argument. It turns out that this is correct of course.

[swansont]

Here’s the idea; energy is distance times force (E=DF), and force is mass times acceleration (E=DMA), and acceleration is velocity over time, which is the same as distance over time squared (E = DMD/T² = MD²/T²).

So energy has units of mass times velocity squared. So, if there were some kind of universal relationship between mass and energy, then it should depend on universal constants. Quick! Name a universal speed! E=MC²

 

 

From a physics standpoint all that means is that energy must have units that include mass* speed^2, and kinetic energy is an obvious example. But there's no actual connection to mass at rest being a form of energy, or that multiplication by a constant would necessarily mean anything.

 

Einstein's derivation is in a paper from 1905 entitled DOES THE INERTIA OF A BODY DEPEND UPON ITS ENERGY-CONTENT?

https://www.fourmilab.ch/etexts/einstein/E_mc2/www/

[Schneibster]

I protest; this is not a "quick physics question" but one of the most profound subjects in physics today!

 

Not that that's bad.

[davidivad]

both Ajb and Swansont are correct.

if you want a ride of the bus and not just appease your immediate senses be prepared for the full ride.

be prepared to read the article i presented because the article itself says that this is a "quick and ugly" interpretation.

be sure to read the rest of the article as it goes on to try to tackle all of the important elements involved.

you need to read the resource i gave to understand.

Edited April 9, 2014 by davidivad

[Popcorn Sutton]

Thanks for your answers. Swansont somewhat put my mind to rest on this topic, the rest of you came close to helping it make sense to me but I'm not sure if the equation is just a guide line or a rule.

[swansont]

Thanks for your answers. Swansont somewhat put my mind to rest on this topic, the rest of you came close to helping it make sense to me but I'm not sure if the equation is just a guide line or a rule.

 

It's a rule. An object at rest has an energy of mc^2, rather than zero.

[Popcorn Sutton]

So in a 1g object, it's energy is approx 34,596,000,000 grams?

[Schneibster]

IIRC it's about 20kt/gram of annihilated matter (so a half gram of antimatter would annihilate a half gram of matter, for a total of 1g annihilated). I don't remember the figure in joules but there are numerous conversion calculators on line. It's on the close order of 10 or 20 tJ. It's about 90 tJ.

 

Did you mean "joules" instead of "grams" above? Later: No, you can't possibly. The correct value for the energy of a gram of matter is 89,875,543,056,250 joules or 21.480770329 kilotons. That's about 90 trillion joules, or 21 kilotons in nuclear explosive terms.

Edited April 10, 2014 by Schneibster

[Sensei]

So in a 1g object, it's energy is approx 34,596,000,000 grams?

 

No. And no.

 

Energy is in Joules unit. Which is kg * meter^2 * second^-2

 

1g = 0.001 kg

c= 299792458 m/s

so

E=0.001*299792458^2 = 8.9875517873681764e+13 J

 

To release this energy there would be needed antimatter.

 

Reread what I said in #4 post.

Radioactive decay is splitting particle that is initially at rest, to couple particles with high energy-momentum-velocity.

It's much easier to see mass-energy equivalence when you know how to calculate released energy (decay energy).

 

Edited April 10, 2014 by Sensei