NEET-XII-Physics
11: Gravitation
- #5If the acceleration due to gravity at the surface of the earth is g, the work done in slowly lifting a body of mass m from the earth’s surface to a height R equal to the radius of the earth is
(a)
12mgR
(b)
2mgR
(c)
mgR
(d)
14mgR.digAnsr: aAns : (a) `` \frac{1}{2}mgR``
Work done = `` -``(final potential energy `` -`` initial potential energy)
`` \Rightarrow W=-\left(\frac{GMm}{2R}-\frac{GMm}{R}\right)``
`` \Rightarrow W=\frac{1}{2}\frac{GMm}{R}=\frac{1}{2}mR\times \left(\frac{GM}{{R}^{2}}\right)``
`` \Rightarrow W=\frac{1}{2}mRg\left[\because g=\frac{GM}{{R}^{2}}\right]``
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