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JEE Main 2015 (11 Apr, Shift 1) · Gravitational Potential & Energy

Gravitational Potential & Energy question from JEE Main 2015 (11 Apr, Shift 1)

Q26JEE Main 2015 · 11 APR · SHIFT 1Medium

Gravitational Potential & Energy

Which of the following most closely depicts the correct variation of the gravitation potential V(r) due to a large planet of radius R and uniform mass density? (figuresarenotdrawntoscale)

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Answer: (b)

  1. Inside: V=−GM(3R2−r2)2R3V = -\frac{GM(3R^2 - r^2)}{2R^3}, a parabola with minimum −3GM2R-\frac{3GM}{2R} and zero slope at the centre.
  2. Outside: V=−GMrV = -\frac{GM}{r}, negative and rising towards zero.
  3. Potential is negative everywhere, smooth at RR, flat-bottomed at r=0r = 0.
  4. So the answer is (b).
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