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JEE Main 2023 (30 Jan, Shift 1) · Gravitational Potential & Energy

Gravitational Potential & Energy question from JEE Main 2023 (30 Jan, Shift 1)

Q11JEE Main 2023 · 30 JAN · SHIFT 1Medium

Gravitational Potential & Energy

If the gravitational field in the space is given as (−Kr2)\left(-\frac{K}{r^2}\right). Taking the reference point to be at r=2 cmr = 2\text{ cm} with gravitational potential V=10 J/kgV = 10\text{ J/kg}. Find the gravitational potential at r=3 cmr = 3\text{ cm} in SI unit (Given, that K=6 J cm/kgK = 6\text{ J cm/kg})

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Answer: (b)

  1. dVdr=−E=Kr2⇒V(r)=−Kr+C\frac{dV}{dr} = -E = \frac{K}{r^2} \Rightarrow V(r) = -\frac{K}{r} + C
  2. At r=2r = 2 cm: 10=−62+C⇒C=1310 = -\frac{6}{2} + C \Rightarrow C = 13
  3. At r=3r = 3 cm: V=−63+13=11 J/kgV = -\frac{6}{3} + 13 = 11\ \text{J/kg}
  4. So the answer is (b) 11.
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