A ring of mass `m_(1)` and radius R is fixed in space at some location. An external agent brings a point mass `m_(2)` from infinity to centre of the ring. Work done by the external agent will beA. `-(Gm_(1)m_(2))/(R)`B. `(Gm_(1)m_(2))/(R)`C. `(Gsqrt(m_(1)^(2)+m_(2)^(2)))/(R)`D. `(Gm_(1)m_(2))/(R(m_(1)^(2)+m_(2)^(2)))`

A ring of mass `m_(1)` and radius R is fixed in space at some location

1.	A ring of mass `m_(1)` and radius R is fixed in space at some location. An external agent brings a point mass `m_(2)` from infinity to centre of the ring. Work done by the external agent will beA. `-(Gm_(1)m_(2))/(R)`B. `(Gm_(1)m_(2))/(R)`C. `(Gsqrt(m_(1)^(2)+m_(2)^(2)))/(R)`D. `(Gm_(1)m_(2))/(R(m_(1)^(2)+m_(2)^(2)))`
Answer» Correct Answer - A Work done, `W=DeltaU=U_(f)-U_(i)=U_(f)("as " U_(i)=0)` `rArr W = -(Gm_(1)m_(2)//R)`.

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