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My book says that minimum energy required to remove the satellite from its orbit is equal to its total energy (K.E+P.E). But shouldn't it equal to only the potential energy difference of satellite in orbit and at infinity since Kinetic energy need not be zero.

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The energy required by the body will be given by:

$$\Delta E = (U_2 + K_2) - (U_1 + K_1)$$

Since $U_2=0$, the energy required by the body is

$$\Delta E = K_2 -U_1 -K_1$$

Since Gravitational potential energy is negative and Kinetic energy is positive, the $-K_1$ actually helps reduce the energy required to remove the satellite from its orbit. Also, it's obvious that $K_2$ needs to be zero if we want to minimize the energy required.

Hence, the minimum energy required will be $-(K_1 + U_1)$

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