Question

Find the work done to take a particle of mass m from surface of the earth to a height equal to 2R -

• A. 2 mg R
• B. $\frac{mgR}{2}$
• C. 3 mg R
• D. $\frac{2mgR}{3}$

Answer 1

Answer: (D)

$\frac{2mgR}{3}$

Answer 2

W = D(PE) = GMm $\left\lbrack \frac{1}{R}–\frac{1}{3R} \right\rbrack$

= $\frac{2GMm}{3R}$ = $\frac{2}{3}$ gm R