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⚛️ Physics  ·  Gravitation  ·  NEET & JEE

A satellite is in circular orbit. When it loses energy due to air resistance, its orbital speed:

Answer: Increases.

  • A Decreases
  • B Increases
  • C Stays same
  • D Oscillates

Correct answer: B. Increases

Explanation: When energy decreases, satellite moves to lower orbit (smaller r). Since v = sqrt(GM/r), smaller r means higher speed. Paradoxically, losing energy makes it speed up.

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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