Mass Really Does Increase with Speed

# Mass Really Does Increase with Speed - greater forces for...

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Mass Really Does Increase with Speed Deciding that masses of objects must depend on speed like this seems a heavy price to pay to rescue conservation of momentum! However, it is a prediction that is not difficult to check by experiment. The first confirmation came in 1908, measuring the mass of fast electrons in a vacuum tube. In fact, the electrons in an old-fashioned color TV tube are about half a percent heavier than electrons at rest, and this must be allowed for in calculating the magnetic fields used to guide them to the screen. Much more dramatically, in modern particle accelerators very powerful electric fields are used to accelerate electrons, protons and other particles. It is found in practice that these particles become heavier and heavier as the speed of light is approached, and hence need greater and
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Unformatted text preview: greater forces for further acceleration. Consequently, the speed of light is a natural absolute speed limit. Particles are accelerated to speeds where their mass is thousands of times greater than their mass measured at rest, usually called the “rest mass”. Warning : It should be mentioned that some people don’t like the statement that mass increases with speed, they feel that the word “mass” should be restricted to the rest mass of an object, which we’ve called m . This difference of definition has no physical content, however—it’s just a matter of taste. We would write momentum as p = mv , they would write our m as m , and say the formula for momentum in their notation is Either way, a fast electron is that much harder to deflect from a straight line....
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