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⚛️ Physics  ·  Gravitation  ·  NEET & JEE

A satellite at radius r from Earth center has angular momentum L. If radius decreases to r/4 (no external torque), new angular momentum is:

Answer: L.

  • A L/4
  • B L/2
  • C L
  • D L/16

Correct answer: C. L

Explanation: No external torque means angular momentum is conserved. L = constant regardless of r change.

Variation of g with Height and Depthgg_surfaceAbove surface: g ∝ 1/r² (falls off curving down)Below surface: g ∝ r (falls off LINEARLY)Earth's surface (r = R)centre (r=0): g=0g is MAXIMUM exactly at the surface - it decreases in both directions, but by different laws

g is maximum at Earth's surface; going up, it falls off as 1/r² (inverse-square); going down, it falls off linearly with depth (since only the mass enclosed within radius r contributes), reaching zero at the centre.

Concept context

Universal gravitation, orbital mechanics, gravitational potential, and escape velocity.

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