Question

If mass increases the closer an object gets to the speed of light, what would be the new mass of a 1kilogram object at 99.9% of the speed of light?

Answer 1

According to the theory of special relativity, an object's relativistic mass increases as it approaches the speed of light ($c$). The formula for calculating relativistic mass is:

$m_{\text{rel}}=\frac{m_0}{\sqrt{1-\frac{v^2}{c^2}}}$

Where: $m_{\text{rel}}$ is the relativistic mass of the object, $m_0$ is the rest mass of the object (mass at rest, i.e., when its velocity is zero), $v$ is the velocity of the object, and $c$ is the speed of light in a vacuum.

In this case, $m_0=1$ kilogram (the rest mass of the object) and $v=0.999\times <$