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← JEE Main 2014 · 19 Apr · Shift 1
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JEE Main 2014 · 19 Apr · Shift 1, Physics question 7

The gravitational field in a region is given by g⃗=5 N/kg i^+12 N/kg j^\vec g=5\text{ N/kg}\,\hat i+12\text{ N/kg}\,\hat j. The change in the gravitational potential energy of a particle of mass 2 kg when it is taken from the origin to a point (7 m, −3 m) is :

Choose one option
Answer and worked solution

Official answer: Bonus: full marks to everyone

The field does work W=m g⃗⋅r⃗=2 (5×7+12×(−3))=−2W=m\,\vec g\cdot\vec r=2\,(5\times7+12\times(-3))=-2 J, so
ΔU=−W=+2 J.\Delta U=-W=+2\text{ J}.
None of the options is +2 J, and the question was given marks to all.

Topics:Gravitational field and potential
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