Relativistic Energy: E = mc²

Einsteins most famous formula

Test 6 of Einstein Logic Test


A body in vacuum with mass of 1 kg is dropped at position h1, so that it falls 1 m down to earth. After 1 m falling down (position h2)  the body has a speed of roundabout 4.43 m/s due to gravitational acceleration of 9,81 m/s².

Test question 6:

Which velocities  v(h1) and v(h2) of the body have to be taken in both positions for calculation of the energy of the body? The generally accepted formula for the relativistic energy (rest energy +  kinetic energy) is

E = m * c² * Lorentz-factor

Lorentz-factor = 1/ square-root (1- (v² / c²)) ; m = rest mass, c = constant light speed


Choice of test answers:

A) v(h1) = 0 m/s, v(h2) = 4,43 m/s

B) As according to principle of relativity absolute velocities are not known you can take the reference frame of the earth surface as in A), but you also can take any other reference frame.

C) As according to the principle of energy conservation the energy has to be constant in both positions , you have to take in both cases the rest frame with 0 m/s. 

D) All velocities have to be referred to the corresponding energetic relevant reference frame, which is different from earth surface

E) Question can't be answered because there is no physical definition for relativistic energy



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