NEET-XII-Physics
11: Gravitation
- #6A person brings a mass of 1 kg from infinity to a point A. Initially the mass was at rest but it moves at a speed of 2 m s -1 as it reaches A. The work done by the person on the mass is -3 J. The potential at A is
(a) -3 J kg-1
(b) -2 J kg-1
(c) -5 J kg-4
(d) none of these.digAnsr: dAns : The work done by the person is equal to the kinetic energy and the potential energy of the mass of 1 kg at point A.
Let VA be the potential at point A.
`` \,\mathrm{\,Now\,},W=\frac{1}{2}m{v}^{2}+{\left(P.E.\right)}_{\,\mathrm{\,A\,}}``
`` \Rightarrow W=\frac{1}{2}m{v}^{2}+{V}_{\,\mathrm{\,A\,}}\times m``
`` \Rightarrow -3=\frac{1}{2}\times 1\times (2{)}^{2}+{V}_{\,\mathrm{\,A\,}}\times 1``
`` \Rightarrow {V}_{\,\mathrm{\,A\,}}=-5\,\mathrm{\,J\,}/\,\mathrm{\,Kg\,}``
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