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7.Gravitation
medium
The minimum energy required to launch a satellite of mass $m$ from the surface of earth of mass $M$ and radius $R$ in a circular orbit at an altitude of $2 R$ from the surface of the earth is:
A
$\frac{2 G m M}{3 R}$
B
$\frac{G m M}{2 R}$
C
$\frac{G m M}{3 R}$
D
$\frac{5 G m M}{6 R}$
(NEET-2024)
Solution
Apply energy conservation,
$U_I+K_I=U_f+K_f$
$\Rightarrow \quad-\frac{G M m}{R}+K_I=-\frac{G M m}{3 R}+\frac{1}{2} m v^2$
$\Rightarrow \quad-\frac{G M m}{R}+K_I=-\frac{G M m}{3 R}+\frac{1}{2} \times m \times \frac{G M}{3 R}$
$\Rightarrow \quad K_I=-\frac{1}{6} \frac{G M m}{R}+\frac{G M m}{R}$
$K_I=\frac{5}{6} \frac{G M m}{R}$
Standard 11
Physics