How to simply solve for E=MC^2?

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    E=mc^2
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Discussion Overview

The discussion revolves around the equation E=mc², specifically how to solve for energy (E) and the correct interpretation of the equation. Participants explore the relationship between mass, the speed of light, and energy, while addressing unit consistency and the context of the calculations.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant suggests that to solve for E, you multiply mass by the speed of light squared, but questions the units used (miles per second).
  • Another participant clarifies that energy divided by time is power, emphasizing the need for consistent units.
  • There is a discussion about whether the squaring applies to the product of mass and speed of light or just the speed of light itself, with some participants asserting that it should only be the speed of light that is squared.
  • One participant notes that E=mc² represents the total energy content of an object at rest, not the power it can produce per second.
  • Another participant points out that the equation is already solved for E, indicating it is expressed as E=something.
  • There is a mention of the need for context regarding the calculation, as it may not yield meaningful results in many circumstances.
  • A participant explains that knowing the rest mass allows for straightforward calculation of energy using the equation, while also discussing the concept of power in relation to energy differences over time.
  • A younger participant expresses a desire to understand the logic behind the equation and confirms their age, indicating a learning perspective.

Areas of Agreement / Disagreement

Participants express various interpretations of the equation and its application, with no consensus reached on the correct approach to solving for E or the implications of the calculations. Multiple competing views remain regarding the squaring of terms and the context of the energy calculation.

Contextual Notes

Participants highlight the importance of unit consistency and the distinction between energy and power. There are unresolved questions about the context in which the calculations are meaningful and the assumptions underlying the discussion.

Zarich12
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I was wondering how to simply solve for E=MC^2. I have basic idea but I just want to check it. You take the mass times the speed of light (in miles per second?) and square that. Over one second that is equal to the number of watts the object could produce. Is that right. If there are any mistakes there please let me know. Thanks!
 
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Solve for what?
You can divide or multiply the equations by the speed of light or any other non-zero variables as often as you want. It does not matter which system of units you use, as long as you keep them consistent.

Energy divided by time is power, right.
 
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Solve for E in that equation, but yes, that answers my question. I just wanted to make sure i was running the computations correctly. Thanks!
 
Zarich12 said:
You take the mass times the speed of light (in miles per second?) and square that. Over one second that is equal to the number of watts the object could produce.

If you're measuring energy in joules and power in watts, you'll need to use meters for distances and meters per second for speeds.
 
And no, it is not the power you can produce per second with an object. It is the total energy content of the object if it is at rest.
 
Also, it's not clear if you're squaring the result of mass times speed of light (which is incorrect) or just the speed of light (which is correct).
 
Zarich12 said:
Solve for E in that equation, but yes, that answers my question. I just wanted to make sure i was running the computations correctly. Thanks!
The equation is solved for E already: it is "E=something".
 
Bandersnatch said:
Also, it's not clear if you're squaring the result of mass times speed of light (which is incorrect) or just the speed of light (which is correct).
In more explicit mathematical terms, ##mc^2## means ##m(c^2)## not ##(mc)^2##.
 
Nugatory said:
If you're measuring energy in joules and power in watts, you'll need to use meters for distances and meters per second for speeds.
Right, sorry about that. I meant meters.
 
  • #10
Bandersnatch said:
Also, it's not clear if you're squaring the result of mass times speed of light (which is incorrect) or just the speed of light (which is correct).
Just the speed of light.
 
  • #11
jtbell said:
In more explicit mathematical terms, ##mc^2## means ##m(c^2)## not ##(mc)^2##.
Right, and given that you know only to square the speed of light, not the entire equation.
 
  • #12
Why are you interested, by the way? As Orodruin notes, there are relatively few circumstances where this calculation would give you a meaningful power output. You may be using one of them, but you may not. A spot of context would enable us to comment.
 
  • #13
Zarich12 said:
Right, and given that you know only to square the speed of light, not the entire equation.
then you have 1 equation with 2 unknowns as a result it does not have 1 solution. It's exactly the same as y= ax if you know a. If you know neither y,x then this equation is solved by an infinite set of y,x which lie on a line with slope a.
As things are you are only confusing yourself; what's the question you want to answer?
If you know the rest mass you input it in m (in kg) and multiplying with the c^2 (in m/s) you can obtain the energy E (in Joule) of that mass at rest. It's not an equation that needs a lot to be solved.
In order to speak for radiated away power, you must have an energy difference \Delta E = E_{fin}-E_{init} in some time interval \Delta t = t_{fin} - t_{init}:
Power= \frac{\Delta E}{\Delta t}
The only way to have some \Delta E is if your mass is changing with respect to time: (\Delta m= m_{fin} - m_{init} \ne 0.)
 
Last edited:
  • #14
I know it doesn't have much to be solved. I just wanted to make sure I was doing it right. I'm thirteen, so I just wanted to make sure I understood the logic behind the equation.
 

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