Arsenic&Lace said:Here's my stupid question: In the mass equation from SR, we have the m0 term for rest mass; but how would you determine the rest mass of an object? Isn't an object on the earth, which is in motion, also in motion? So wouldn't the mass of an object on Earth not actually be its mass at rest?
Thanks in advance!
PAllen said:All you need to measure rest mass directly is to not be in motion relative to the object you are measuring. It doesn't matter at all that you and the object are moving relative to something else (e.g. the sun).
Arsenic&Lace said:Thanks! If you don't mind, another question: why is this the case?
The mass equation in special relativity is given by m = m0/√(1 - v2/c2), where m is the rest mass of a moving object, m0 is the rest mass of the object at rest, v is the velocity of the object, and c is the speed of light.
The rest mass of a moving object can be determined by measuring its velocity and using the mass equation in special relativity. The rest mass is the value of m when v is equal to 0. This can be calculated by setting v = 0 in the equation and solving for m.
The difference in the rest mass of a moving object and its mass at rest is due to the effects of special relativity. As an object approaches the speed of light, its mass increases due to the dilation of time and contraction of length. This results in a higher rest mass compared to its mass at rest.
No, the mass equation in special relativity only applies to objects with rest mass. Massless particles, such as photons, have no rest mass and therefore cannot be described using this equation.
The mass equation in special relativity is a rearrangement of Einstein's famous equation, E = mc2. In this equation, E represents energy, m represents mass, and c represents the speed of light. When v = 0, the mass equation reduces to E = m0c2, which is the famous equation introduced by Einstein in his theory of special relativity.