How to simply solve for E=MC^2?

  • Context: High School 
  • Thread starter Thread starter Zarich12
  • Start date Start date
  • Tags Tags
    E=mc^2
Click For Summary
SUMMARY

The discussion centers on the correct interpretation and application of the equation E=mc², specifically addressing how to calculate energy (E) from mass (m) and the speed of light (c). Participants clarify that the equation is already solved for E, indicating that E equals mass multiplied by the square of the speed of light. They emphasize the importance of using consistent units, specifically meters for distance and seconds for time, to accurately compute energy in joules. Additionally, they highlight the distinction between calculating total energy content at rest versus power output over time.

PREREQUISITES
  • Understanding of the equation E=mc²
  • Basic knowledge of units of measurement (meters, seconds, joules)
  • Familiarity with the concept of energy and power
  • Mathematical skills for manipulating equations
NEXT STEPS
  • Study the implications of E=mc² in physics
  • Learn about unit conversions in physics, particularly between joules and watts
  • Explore the concept of rest mass and its significance in energy calculations
  • Investigate scenarios where mass-energy equivalence is applicable
USEFUL FOR

This discussion is beneficial for students learning physics, educators teaching energy concepts, and anyone interested in the foundational principles of mass-energy equivalence.

Zarich12
Messages
18
Reaction score
0
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!
 
Physics news on Phys.org
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.
 
  • Like
Likes   Reactions: Zarich12
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.
 

Similar threads

  • · Replies 16 ·
Replies
16
Views
2K
  • · Replies 14 ·
Replies
14
Views
2K
  • · Replies 55 ·
2
Replies
55
Views
6K
  • · Replies 17 ·
Replies
17
Views
2K
  • · Replies 13 ·
Replies
13
Views
7K
  • · Replies 62 ·
3
Replies
62
Views
6K
  • · Replies 124 ·
5
Replies
124
Views
17K
  • · Replies 11 ·
Replies
11
Views
2K
  • · Replies 7 ·
Replies
7
Views
5K
  • · Replies 3 ·
Replies
3
Views
2K