Gravitation Practice Questions

Gravitational potential energy ${\text{E}}=-\;\frac{G M m}{r}$ where $M=$ mass of earth $m=$ mass of body $r=$ radius of earth Energy required to move a body of mass $m$ from an orbit of radius $2 R$ to $3 R$ $=($ Potential energy of the Earth-mass system when mass is at distance $3 R)-$ (Potential energy of the Earth-mass system when mass is at distance $2 R$ ) $=\;\frac{-G M m}{3 R}-(\;\frac{-G M m}{2 R})$ $=\;\frac{-G M m}{3 R}+\;\frac{G M m}{2 R}$ $=\;\frac{-2 G M m+3 G M m}{6 R}=\;\frac{G M m}{6 R}$

When gravitational force of attraction between Earth and a satellite revolving around it becomes zero, then the centripetal force becomes zero. So the satellite will move tangentially to the original orbit with the same velocity as it has at the instant when gravitational force becomes zero.