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A small mass `m` is moved slowly from the surface of the earth to a height `h` above the surface. The work done (by an external agent) in doing this isA. `mgh`, for all values of hB. `mgh`, for `hlt ltR`C. `1//2, mgR`, for `h=R`D. `-1//2mgR`, for `h=R` |
Answer» Correct Answer - B::C `W=U_(2)-U_(1)=(GMm)/(R+h)(-(GMm)/R)=-GMm[1/R-1/(R+h)]` `=gR^(2)m[h/(R(R+h))]=(mgRH)/(R+h)` For `hlt ltR, W=mgh` for `h=R, W=(mgR)/2` |
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