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Title: GR8677.068
Post by: conantee on January 06, 2010, 12:10:28 PM
68. If a newly discovered particle X moves with a speed equal to the speed of light in vacuum, then which of the following must be true?
(A) The rest mass of X is zero.
(B) The spin of X equals the spin of a photon.
(C) The charge of X is carried on its surface.
(D) X does not spin.
(E) X cannot be detected.


Title: Re: GR8677.068
Post by: conantee on October 11, 2010, 12:34:42 PM
The answer is just (A). You can bet that speed-of-light travel is related to relativity. The only choice related to relativity is (A).

The deeper reason is that it requires infinite energy to move an object with non-zero rest mass to the speed of light - simply impossible.

The correct answer is (A). 89 of 100 people answer this question correctly.