Energy required to move a body of mass \(\mathrm{m}\) from from an orbit of radius \(2 \mathrm{R}\) to \(3 \mathrm{R}\) is \(\ldots \ldots \ldots \ldots\) (A) \(\left[(\mathrm{GMm}) /\left(12 \mathrm{R}^{2}\right)\right]\) (B) \(\left[(\mathrm{GMm}) /\left(3 \mathrm{R}^{2}\right)\right]\) (C) \([(\mathrm{GMm}) /(8 \mathrm{R})]\) (D) \([(\mathrm{GMm}) /(6 \mathrm{R})]\)

Short Answer

Expert verified
The energy required to move a body of mass m from an orbit of radius 2R to 3R is \(\Delta U = \frac{GMm}{6R}\). The correct answer is (D).

Step by step solution

01

Calculate Initial Potential Energy

In the initial state, the body is in an orbit of radius 2R. The gravitational potential energy at this radius can be calculated using the formula: \(U_1 = -\frac{GMm}{r_1}\) Substituting the given radius, \(r_1 = 2R\): \(U_1 = -\frac{GMm}{2R}\)
02

Calculate Final Potential Energy

In the final state, the body is in an orbit of radius 3R. The gravitational potential energy at this radius can be calculated using the same formula: \(U_2 = -\frac{GMm}{r_2}\) Substituting the given radius, \(r_2 = 3R\): \(U_2 = -\frac{GMm}{3R}\)
03

Find the Difference in Potential Energy

The energy required to move the body from radius 2R to 3R is the difference in potential energy between the two orbits: \(\Delta U = U_2 - U_1\) Substituting the values we calculated for \(U_1\) and \(U_2\): \(\Delta U = -\frac{GMm}{3R} - \left(-\frac{GMm}{2R}\right)\)
04

Simplify the Expression

Now we simplify the expression for the change in potential energy: \(\Delta U = \frac{GMm}{2R} - \frac{GMm}{3R} = \frac{3GMm - 2GMm}{6R} = \frac{GMm}{6R}\)
05

Match the Answer with the Given Options

Matching the expression we found for the change in potential energy with the answer options given in the exercise, we find that the correct answer is: \(\Delta U = [(GMm) /(6R)]\) So, the correct answer is (D).

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