“Proof” of E=mc2
Before Einstein, it was known that a beam of light pushes against matter; this is known as radiation pressure. This means the light has momentum. A beam of light of energy E has momentum E/c. Einstein used this fact to show that radiation (light) energy has an equivalent mass.
Consider a cylinder of mass M (see accompanying figure-“energy”).
A pulse of light with energy E is emitted from the left side. The cylinder recoils to the left with velocity v=E/(Mc).
If the mass of the cylinder is large, it doesn’t move far before the light reaches the other side. So, the light must travel a distance L, requiring time t=L/c. In this time, the cylinder travels a distance x=vt=[E/(Mc)](L/c).
Einstein reasoned that the center of mass of an isolated system doesn’t just move on its own. So, the motion of the cylinder must be compensated by the motion of some other mass. Let’s assume the light has mass m. Then, Mx=mL, since the cylinder moves x to the left and the light moves L to the right. Substituting the expression for x given above, the equation can be simplified to E=mc2.
From the fact that light has momentum, Einstein showed that light energy has the characteristics of mass also. In other words, energy has inertia. It turns out that all energy has this feature. That’s because one form of energy can be transformed into another. So, if one kind of energy has this characteristic, all forms of energy do.
The Essay on Energy Mass Light Einstein
-- Exhibit Contents -- Exhibit HOME Formative Years The Great Works - 1905 World Fame Public Concerns Quantum and Cosmos Nuclear Age Science and Philosophy 'The World As I See It More About Einstein Site Contents 'In light of knowledge attained, the happy achievement seems almost a matter of course, and any intelligent student can grasp it without too much trouble. But the years of anxious ...
Einstein himself explains the meaning of E=mc2 in this sound clip.
The fine print: The word proof is in quotes above because this is not truly a rigorous proof. Simplifications and approximations were made to facilitate understanding. Some of these are easy to eliminate at the expense of a little more algebra. Some of them are of a more fundamental nature and require significant modification of the gedankenexperiment. However, the basic concepts are correct and this “proof” conveys the essence of the connection between mass and energy.
http://www.drphysics.com/syllabus/syllabus.html
A frame of reference in physics, may refer to a coordinate system or set of axes within which to measure the position, orientation, and other properties of objects in it, or it may refer to an observational reference frame tied to the state of motion of an observer. It may also refer to both an observational reference frame and an attached coordinate system, as a unit.
In Newtonian physics and special relativity, an inertial frame of reference (or Galilean reference frame) is a frame of reference in which Newton’s first law of motion applies: an object moves at a constant velocity unless acted on by an external force. All inertial frames are in a state of constant, rectilinear motion with respect to one another; they are not accelerating (in the sense of proper acceleration that would be detected by an accelerometer).
Measurements in one inertial frame can be converted to measurements in another by a simple transformation (the Galilean transformation in Newtonian physics and the Lorentz transformation in special relativity).
In general relativity, an inertial reference frame is only an approximation that applies in a region that is small enough for the curvature of space to be negligible. [1][2]
Physical laws take the same form in all inertial frames.[3] In a non-inertial reference frame the laws of physics depend upon the particular frame of reference, and the usual physical forces must be supplemented by fictitious forces. [4] [5] For example, a ball dropped towards the ground does not go exactly straight down because the Earth is rotating. Someone rotating with the Earth must include the Coriolis force to predict the horizontal motion. Another example of a fictitious force associated with rotating reference frames is the centrifugal force.
The Review on Frames Of Reference In Occupational Therapy
Theoretical AssumptionsHuman development occurs in an orderly fashion throughout the cycleSteps within the developmental process are sequential and none can be skipped. As a person proceeds through the life cycle, he encounters life events and changing internal and external conditions that necessitate reappraisal and change. As in life, during treatment the patient has responsibility for his own ...
In biochemistry, metabolic pathways are series of chemical reactions occurring within a cell. In each pathway, a principal chemical is modified by a series of chemical reactions. Enzymes catalyze these reactions, and often require dietary minerals, vitamins, and other cofactors in order to function properly. Because of the many chemicals (a.k.a. “metabolites”) that may be involved, metabolic pathways can be quite elaborate. In addition, numerous distinct pathways co-exist within a cell. This collection of pathways is called the metabolic network. Pathways are important to the maintenance of homeostasis within an organism. Catabolic (break-down) and Anabolic (synthesis) pathways often work interdependently to create new biomolecules as the final end-products.
A metabolic pathway involves the step-by-step modification of an initial molecule to form another product. The resulting product can be used in one of three ways:
* To be used immediately, as the end-product of a metabolic pathway
* To initiate another metabolic pathway, called a flux generating step
* To be stored by the cell
