Answer 1

Mass of a particle depends on the relativistic speed v with which it moves as 

\[m = \frac{m_o}{\sqrt{1 - \frac{v^2}{c^2}}}\]

The gravitational force of attraction of Earth is given by

\[F = \frac{GMm}{r^2}\]

\[ \Rightarrow F = \frac{GM m_o}{r^2 \sqrt{1 - \frac{v^2}{c^2}}}\]