Science
Related: About this forumOk brainiacs...someone help me...
In regards to E = MC2... I am trying to find a simple working example to how this theory is used.
I'm going to spin out a very simple scenario
ex: trying to determine the E (energy) contained in a 1 lb steel ball
1. By which yardstick is E determined ? Kilo Watt? Something else?
2. If E = MC2...I imagine that the first thing to determine is the mass of the ball.
Is this determined by weight? By size?...and more importantly...what unit of weight
or size measurement would you use for your calculations? Lbs? Ounces? Kilo grams?
3. C2 (speed of light squared) What unit of speed measurement would you use for your calculation?
MP hour? MP sec? Light years?
4. All of the variables listed would have a great impact on calculating E
ok...all that being said please fill in the blanks below with actual figures for me.
Energy of 1 lb steel ball E____= M______C2_______
sharp_stick
(14,400 posts)All measurements are in metric (SI) units and you should be able to plug your data in.
annavictorious
(934 posts)here's a website that might help you sort things out.
http://www.emc2-explained.info/Emc2/Equation.htm#.V302BxKukjG
Jim__
(14,045 posts)... c**2 (9* 10**16 meters**2 per second**2)
That's what I get from that website.
90,000,000,000,000,000 joules
clarice
(5,504 posts)longship
(40,416 posts)Which means that the most accurate formulation of the famous equation may be:
m = E/c^2
Not the more familiar algebraic equivalent:
E = mc^2
These apply only to a body at rest.
Nobel laureate Frank Wilczek puts it this way:
can some of a body's mass arise from the energy of the stuff it contains? Right from the start Einstein was thinking about the conceptual foundations of physics, not about the possibility of making bombs or reactors.
The concept of energy is much more central to modern physics than the concept of mass. This shows up in many ways. It is energy, not mass, that is truly conserved. It is energy that appears in our fundamental equations, such as Boltzmann's equation for statistical mechanics, Schrödinger's equation for quantum mechanics, and Einstein's equation for gravity.
(From Wilczek's book, The Lightness of Being: Mass, Ether, and the Unification of Forces, a good read if one has interest in such cutting edge things.)
Concerning units, conventionally one uses SI units in science (traditionally, meters, kilograms, seconds). Particle physicists use a more convenient system of units for them, where c = 1 light-second/sec and E = m, both measured in electron-volts.
DetlefK
(16,423 posts)E^2 = (mc^2)^2 + (pc)^2 rules!!!
longship
(40,416 posts)I'll add that it is not a quantum formulation, which IMHO would just confuse an answer to the OPer's clear questions.
DetlefK
(16,423 posts)1.
Energy measured in Joule, mass measured in kg, speed measured in m/s. That's the SI-system of units of measurement. (There is also the CGS-system, but I find that wholly confusing even though it's supposed to be simpler.)
Joule = kg * m^2 / s^2
2.
Easy examples to get a grip for E=mc^2 are nuclear processes. (Important note: Fusing atomic cores lighter than iron produces energy. Fusing cores heavier than iron costs energy. Cracking atomic cores lighter than iron costs energy, cracking atomic cores heavier than iron produces energy.)
Let's take for example nuclear fission: The atomic core of Uranium has a certain weight. Then it decays radioactively and splits into several particles. The weight of all the particles summed up is still not the weight of the original Uranium-core. That difference in energy is emitted as kinetic energy and as electromagnetic radiation.
This energy that is set free and converted from mass into something usable, that is what drives nuclear reactors and this is where the output of nuclear explosions comes from.
3.
Example: Let's say you have a capacitor with a capacity of 1 Farad, and you charge it at a voltage of 1000 volt. Then the capacitor stores an energy of E = 1/2 * C * V^2 = 500,000 J
c is 300,000 km/s = 300,000,000 m/s
5*10^5 J = m * (3*10^8 m/s)^2 = m * 9 * 10^16 m^2 / s^2
=> 0.56 * 10^-11 kg = m
So a capacitor storing this much energy will be ~5.6 nano-gramms heavier than an empty capacitor. (A grain of salt is about 1 milli-gramm.)
clarice
(5,504 posts)bvf
(6,604 posts)Last edited Sun Jul 10, 2016, 08:47 PM - Edit history (2)
but an intro to dimensional analysis might be helpful to you.
How fast do your fingernails grow in miles per hour?
Hint: there's an answer, just as there's an answer to the question of how fast you might be driving in furlongs/fortnight.
ETA:
I guess what I'm saying here is that units of measurement are NOT variables.
You can measure your height in centimeters, feet, inches, or what have you. Your confusion seems to stem from thinking that it can be measured in anything but units of length, and your question takes on the quality of that of someone wondering how old s/he is in foot-pounds.
Relieved to see zero recs here.